diff --git a/fuzzers/007-timing/csv_group2flat.py b/fuzzers/007-timing/csv_group2flat.py
index a80c11ac..a9bd79ac 100644
--- a/fuzzers/007-timing/csv_group2flat.py
+++ b/fuzzers/007-timing/csv_group2flat.py
@@ -6,36 +6,48 @@ from timfuz import Benchmark, loadc_Ads_bs, load_sub, Ads2bounds, corners2csv, c
 def gen_flat(fns_in, sub_json, corner=None):
     Ads, bs = loadc_Ads_bs(fns_in, ico=True)
     bounds = Ads2bounds(Ads, bs)
-    zeros = set()
+    # Elements with zero delay assigned due to sub group
+    group_zeros = set()
+    # Elements with a concrete delay
     nonzeros = set()
 
+    if corner:
+        zero_row = [None, None, None, None]
+        zero_row[corner_s2i[corner]] = 0
+    else:
+        zero_row = None
+
     for bound_name, bound_bs in bounds.items():
         sub = sub_json['subs'].get(bound_name, None)
-        if sub:
+        if bound_name in sub_json['zero_names']:
+            if zero_row:
+                yield bound_name, 0
+        elif sub:
+            print('sub', sub)
             # put entire delay into pivot
             pivot = sub_json['pivots'][bound_name]
-            assert pivot not in zeros
+            assert pivot not in group_zeros
             nonzeros.add(pivot)
             non_pivot = set(sub.keys() - set([pivot]))
             #for name in non_pivot:
             #    assert name not in nonzeros, (pivot, name, nonzeros)
-            zeros.update(non_pivot)
+            group_zeros.update(non_pivot)
             yield pivot, bound_bs
         else:
             nonzeros.add(bound_name)
             yield bound_name, bound_bs
     # non-pivots can appear multiple times, but they should always be zero
     # however, due to substitution limitations, just warn
-    violations = zeros.intersection(nonzeros)
+    violations = group_zeros.intersection(nonzeros)
     if len(violations):
         print('WARNING: %s non-0 non-pivot' % (len(violations)))
 
     # XXX: how to best handle these?
     # should they be fixed 0?
-    if corner:
-        zero_row = [None, None, None, None]
-        zero_row[corner_s2i[corner]] = 0
-        for zero in zeros - violations:
+    if zero_row:
+        print('zero_row', len(group_zeros), len(violations))
+        for zero in group_zeros - violations:
+            print('zero', zero)
             yield zero, zero_row
 
 
diff --git a/fuzzers/007-timing/rref.py b/fuzzers/007-timing/rref.py
index 1c665dd0..18a60a67 100644
--- a/fuzzers/007-timing/rref.py
+++ b/fuzzers/007-timing/rref.py
@@ -9,6 +9,20 @@ import sympy
 from collections import OrderedDict
 from fractions import Fraction
 
+def rm_zero_cols(Ads, verbose=True):
+    removed = OrderedSet()
+
+    print('Removing ZERO elements')
+    for row_ds in Ads:
+        for k in set(row_ds.keys()):
+            if k in removed:
+                del row_ds[k]
+            elif k.find('ZERO') >= 0:
+                del row_ds[k]
+                removed.add(k)
+                if verbose:
+                    print('  Removing %s' % k)
+    return removed
 
 def fracr_quick(r):
     return [Fraction(numerator=int(x), denominator=1) for x in r]
@@ -20,14 +34,13 @@ def fracm_quick(m):
     print('fracm_quick type: %s' % t)
     return [fracr_quick(r) for r in m]
 
-
 class State(object):
-    def __init__(self, Ads, drop_names=[]):
+    def __init__(self, Ads, zero_names=[]):
         self.Ads = Ads
         self.names = index_names(self.Ads)
 
         # known zero delay elements
-        self.drop_names = OrderedSet(drop_names)
+        self.zero_names = OrderedSet(zero_names)
         # active names in rows
         # includes sub variables, excludes variables that have been substituted out
         self.base_names = OrderedSet(self.names)
@@ -46,30 +59,34 @@ class State(object):
                 "    Largest: %u" % max([len(x) for x in self.subs.values()]))
         print("  Rows: %u" % len(self.Ads))
         print(
-            "  Cols (in): %u" % (len(self.base_names) + len(self.drop_names)))
+            "  Cols (in): %u" % (len(self.base_names) + len(self.zero_names)))
         print("  Cols (preprocessed): %u" % len(self.base_names))
-        print("    Drop names: %u" % len(self.drop_names))
+        print("    ZERO names: %u" % len(self.zero_names))
         print("  Cols (out): %u" % len(self.names))
         print("  Solvable vars: %u" % len(self.names & self.base_names))
         assert len(self.names) >= len(self.subs)
 
     @staticmethod
-    def load(fn_ins, simplify=False, corner=None):
+    def load(fn_ins, simplify=False, corner=None, rm_zero=False):
+        zero_names = OrderedSet()
+
         Ads, b = loadc_Ads_b(fn_ins, corner=corner, ico=True)
+        if rm_zero:
+            zero_names = rm_zero_cols(Ads)
         if simplify:
             print('Simplifying corner %s' % (corner, ))
             Ads, b = simplify_rows(Ads, b, remove_zd=False, corner=corner)
-        return State(Ads)
+        return State(Ads, zero_names=zero_names)
 
 
 def write_state(state, fout):
     j = {
         'names':
         OrderedDict([(x, None) for x in state.names]),
-        'drop_names':
-        list(state.drop_names),
+        'zero_names':
+        sorted(list(state.zero_names)),
         'base_names':
-        list(state.base_names),
+        sorted(list(state.base_names)),
         'subs':
         OrderedDict([(name, values) for name, values in state.subs.items()]),
         'pivots':
@@ -172,11 +189,11 @@ def state_rref(state, verbose=False):
     return state
 
 
-def run(fnout, fn_ins, simplify=False, corner=None, verbose=0):
+def run(fnout, fn_ins, simplify=False, corner=None, rm_zero=False, verbose=0):
     print('Loading data')
 
     assert len(fn_ins) > 0
-    state = State.load(fn_ins, simplify=simplify, corner=corner)
+    state = State.load(fn_ins, simplify=simplify, corner=corner, rm_zero=rm_zero)
     state_rref(state, verbose=verbose)
     state.print_stats()
     if fnout:
@@ -195,6 +212,7 @@ def main():
     parser.add_argument('--verbose', action='store_true', help='')
     parser.add_argument('--simplify', action='store_true', help='')
     parser.add_argument('--corner', default="slow_max", help='')
+    parser.add_argument('--rm-zero', action='store_true', help='Remove ZERO elements')
     parser.add_argument(
         '--speed-json',
         default='build_speed/speed.json',
@@ -214,6 +232,7 @@ def main():
             fn_ins=fns_in,
             simplify=args.simplify,
             corner=args.corner,
+            rm_zero=args.rm_zero,
             verbose=args.verbose)
     finally:
         print('Exiting after %s' % bench)
diff --git a/fuzzers/007-timing/solve_leastsq.py b/fuzzers/007-timing/solve_leastsq.py
index db22b168..953c4dcf 100644
--- a/fuzzers/007-timing/solve_leastsq.py
+++ b/fuzzers/007-timing/solve_leastsq.py
@@ -30,47 +30,6 @@ def mkestimate(Anp, b):
     return x0
 
 
-def save(outfn, xvals, names, corner):
-    # ballpark minimum actual observed delay is around 7 (carry chain)
-    # anything less than one is probably a solver artifact
-    delta = 0.5
-    corneri = corner_s2i[corner]
-
-    # Round conservatively
-    roundf = {
-        'fast_max': math.ceil,
-        'fast_min': math.floor,
-        'slow_max': math.ceil,
-        'slow_min': math.floor,
-    }[corner]
-
-    print('Writing results')
-    skips = 0
-    keeps = 0
-    with open(outfn, 'w') as fout:
-        # write as one variable per line
-        # this natively forms a bound if fed into linprog solver
-        fout.write('ico,fast_max fast_min slow_max slow_min,rows...\n')
-        for xval, name in zip(xvals, names):
-            row_ico = 1
-
-            # also review ceil vs floor choice for min vs max
-            # lets be more conservative for now
-            if xval < delta:
-                #print('Skipping %s: %0.6f' % (name, xval))
-                skips += 1
-                continue
-            keeps += 1
-            #xvali = round(xval)
-
-            items = [str(row_ico), acorner2csv(roundf(xval), corneri)]
-            items.append('%u %s' % (1, name))
-            fout.write(','.join(items) + '\n')
-    print(
-        'Wrote: skip %u => %u / %u valid delays' % (skips, keeps, len(names)))
-    assert keeps, 'Failed to estimate delay'
-
-
 def run_corner(
         Anp, b, names, corner, verbose=False, opts={}, meta={}, outfn=None):
     # Given timing scores for above delays (-ps)
@@ -140,7 +99,7 @@ def run_corner(
     print('Done')
 
     if outfn:
-        save(outfn, res.x, names, corner)
+        timfuz_solve.solve_save(outfn, res.x, names, corner, verbose=verbose)
 
 
 def main():
diff --git a/fuzzers/007-timing/solve_linprog.py b/fuzzers/007-timing/solve_linprog.py
index 0825bac3..e3e99c18 100644
--- a/fuzzers/007-timing/solve_linprog.py
+++ b/fuzzers/007-timing/solve_linprog.py
@@ -12,50 +12,12 @@ import time
 import timfuz_solve
 
 
-def save(outfn, xvals, names, corner):
-    # ballpark minimum actual observed delay is around 7 (carry chain)
-    # anything less than one is probably a solver artifact
-    delta = 0.5
-    corneri = corner_s2i[corner]
-
-    roundf = {
-        'fast_max': math.ceil,
-        'fast_min': math.floor,
-        'slow_max': math.ceil,
-        'slow_min': math.floor,
-    }[corner]
-
-    print('Writing results')
-    zeros = 0
-    with open(outfn, 'w') as fout:
-        # write as one variable per line
-        # this natively forms a bound if fed into linprog solver
-        fout.write('ico,fast_max fast_min slow_max slow_min,rows...\n')
-        for xval, name in zip(xvals, names):
-            row_ico = 1
-
-            # FIXME: only report for the given corner?
-            # also review ceil vs floor choice for min vs max
-            # lets be more conservative for now
-            if xval < delta:
-                print('WARNING: near 0 delay on %s: %0.6f' % (name, xval))
-                zeros += 1
-                #continue
-            items = [str(row_ico), acorner2csv(roundf(xval), corneri)]
-            items.append('%u %s' % (1, name))
-            fout.write(','.join(items) + '\n')
-    nonzeros = len(names) - zeros
-    print(
-        'Wrote: %u / %u constrained delays, %u zeros' %
-        (nonzeros, len(names), zeros))
-
-
 def run_corner(
         Anp, b, names, corner, verbose=False, opts={}, meta={}, outfn=None):
     if len(Anp) == 0:
         print('WARNING: zero equations')
         if outfn:
-            save(outfn, [], [], corner)
+            timfuz_solve.solve_save(outfn, [], [], corner)
         return
     maxcorner = {
         'slow_max': True,
@@ -180,7 +142,7 @@ def run_corner(
         print('Delay on %d / %d' % (nonzeros, len(res.x)))
 
         if outfn:
-            save(outfn, res.x, names, corner)
+            timfuz_solve.solve_save(outfn, res.x, names, corner, verbose=verbose)
 
 
 def main():
diff --git a/fuzzers/007-timing/timfuz.py b/fuzzers/007-timing/timfuz.py
index a3bc3a1e..540c4abc 100644
--- a/fuzzers/007-timing/timfuz.py
+++ b/fuzzers/007-timing/timfuz.py
@@ -107,6 +107,7 @@ corner_s2i = OrderedDict(
 
 
 def allow_zero_eqns():
+    '''If true, allow a system of equations with no equations'''
     return os.getenv('ALLOW_ZERO_EQN', 'N') == 'Y'
 
 
@@ -732,7 +733,7 @@ def row_sub_vars(row, sub_json, strict=False, verbose=False):
         print(row.items())
 
     delvars = 0
-    for k in sub_json['drop_names']:
+    for k in sub_json['zero_names']:
         try:
             del row[k]
             delvars += 1
@@ -908,3 +909,7 @@ def tilej_stats(tilej):
             print(
                 '  %s: %u / %u solved, %u / %u covered' %
                 (etype, solved, net, covered, net))
+
+def load_bounds(bounds_csv, corner, ico=True):
+    Ads, b = loadc_Ads_b([bounds_csv], corner, ico=ico)
+    return Ads2bounds(Ads, b)
diff --git a/fuzzers/007-timing/timfuz_solve.py b/fuzzers/007-timing/timfuz_solve.py
index de1c5812..b3c43cfb 100644
--- a/fuzzers/007-timing/timfuz_solve.py
+++ b/fuzzers/007-timing/timfuz_solve.py
@@ -1,9 +1,10 @@
 #!/usr/bin/env python3
 
-from timfuz import simplify_rows, loadc_Ads_b, index_names, A_ds2np, run_sub_json, print_eqns, Ads2bounds, instances, SimplifiedToZero, allow_zero_eqns
+from timfuz import simplify_rows, loadc_Ads_b, index_names, A_ds2np, run_sub_json, print_eqns, Ads2bounds, instances, SimplifiedToZero, allow_zero_eqns, corner_s2i, acorner2csv
 from timfuz_massage import massage_equations
 import numpy as np
 import sys
+import math
 
 
 def check_feasible(A_ub, b_ub):
@@ -93,6 +94,44 @@ def filter_bounds(Ads, b, bounds, corner):
     return ret_Ads, ret_b
 
 
+def solve_save(outfn, xvals, names, corner, save_zero=True, verbose=False):
+    # ballpark minimum actual observed delay is around 7 (carry chain)
+    # anything less than one is probably a solver artifact
+    delta = 0.5
+    corneri = corner_s2i[corner]
+
+    roundf = {
+        'fast_max': math.ceil,
+        'fast_min': math.floor,
+        'slow_max': math.ceil,
+        'slow_min': math.floor,
+    }[corner]
+
+    print('Writing results')
+    zeros = 0
+    with open(outfn, 'w') as fout:
+        # write as one variable per line
+        # this natively forms a bound if fed into linprog solver
+        fout.write('ico,fast_max fast_min slow_max slow_min,rows...\n')
+        for xval, name in zip(xvals, names):
+            row_ico = 1
+
+            if xval < delta:
+                if verbose:
+                    print('WARNING: near 0 delay on %s: %0.6f' % (name, xval))
+                zeros += 1
+                if not save_zero:
+                    continue
+            items = [str(row_ico), acorner2csv(roundf(xval), corneri)]
+            items.append('%u %s' % (1, name))
+            fout.write(','.join(items) + '\n')
+    nonzeros = len(names) - zeros
+    print(
+        'Wrote: %u / %u constrained delays, %u zeros' %
+        (nonzeros, len(names), zeros))
+    assert nonzeros, 'Failed to estimate delay'
+
+
 def run(
         fns_in,
         corner,