diff --git a/minitests/roi_harness/defines.v b/minitests/roi_harness/defines.v
deleted file mode 100644
index 1008d558..00000000
--- a/minitests/roi_harness/defines.v
+++ /dev/null
@@ -1,8 +0,0 @@
-`ifndef DIN_N
-`define DIN_N 8
-`endif
-
-`ifndef DOUT_N
-`define DOUT_N 8
-`endif
-
diff --git a/minitests/roi_harness/runme.sh b/minitests/roi_harness/runme.sh
index 4fa2c200..dd97bfe8 100755
--- a/minitests/roi_harness/runme.sh
+++ b/minitests/roi_harness/runme.sh
@@ -1,5 +1,30 @@
 #!/bin/bash
 
+# 12x8 CLBs
+if [ $SMALL = Y ] ; then
+    echo "Design: small"
+    export DIN_N=2
+    export DOUT_N=2
+    export XRAY_ROI=SLICE_X12Y100:SLICE_X27Y111
+# 50x8 CLBs
+else
+    echo "Design: large"
+    export DIN_N=8
+    export DOUT_N=8
+    export XRAY_ROI=SLICE_X12Y100:SLICE_X27Y149
+fi
+
+cat >defines.v <<EOF
+\`ifndef DIN_N
+\`define DIN_N $DIN_N
+\`endif
+
+\`ifndef DOUT_N
+\`define DOUT_N $DOUT_N
+\`endif
+EOF
+
+
 set -ex
 rm -f out_last
 vivado -mode batch -source runme.tcl
diff --git a/minitests/roi_harness/runme.tcl b/minitests/roi_harness/runme.tcl
index bb793082..ac4cc723 100644
--- a/minitests/roi_harness/runme.tcl
+++ b/minitests/roi_harness/runme.tcl
@@ -2,9 +2,9 @@
 # Your ROI should at least have a SLICEL on the left
 
 # Number of package inputs going to ROI
-set DIN_N 8
+set DIN_N "$::env(DIN_N)"
 # Number of ROI outputs going to package
-set DOUT_N 8
+set DOUT_N "$::env(DOUT_N)"
 # How many rows between pins
 # Reduces routing pressure
 set PITCH 3