The 2mm stroke cranks give the transfer too much duration, so this is a good write for the 2mm cranks making a 30.5cc engine. We have twisted some 2mm cranks (like you said), so we went with the sealed G290 crank shaft bearing that replaces the big seal to stabilize the crank more, and we have not twisted one since. Use a Zenoah crank with the 3rd bearing set up, because Zenoah extended the bearing diameter further down the shaft for full support. Previous cranks from Zen and CY have a .001" smaller shaft where the 3rd bearing rides on, but not the current Zen cranks.
The squish band is cut for the proper squish clearance on this kit, and the combustion chamber is cut to give proper compression.