diff --git a/omeroweb/webgateway/marshal.py b/omeroweb/webgateway/marshal.py
index 60f917ded4..010331291d 100644
--- a/omeroweb/webgateway/marshal.py
+++ b/omeroweb/webgateway/marshal.py
@@ -355,8 +355,11 @@ def pixel_size_in_microns(method):
     # NB: some small images like OME-Zarr can have pyramids
     # but these will be ignored
 
-    # TEMP - for A/B testing only use size test if ID is EVEN number!
-    if image.id % 2 == 0 and not image.requiresPixelsPyramid():
+    # TEMP - for A/B/C testing based on image ID
+    big_image = (rv["size"]["width"] * rv["size"]["height"]) > (3000 * 3000)
+    if image.id % 2 == 0 and not big_image:
+        rv["tiles"] = False
+    elif image.id % 2 == 1 and image.requiresPixelsPyramid():
         rv["tiles"] = False
     else:
         if load_re(image, rv):