As Kweasel has pointed out - 2 of the engines that currently have the highest "top end power" (Actual useful torque to turn large props and make large amounts of thrust) are both "under square".

Captinjohn, it sure would be an interesting thread. So many engines have such similar dimensions, there is a plethora of useful parts around. some may require very minor mods to make them work well.

Badazzmax - I have recently used the exact same crank as you to replace an "early JC" one. Didn't try the cylinder change out but it sure makes a good idea for obtaining good quality parts for the future.
(Now I wonder what I could use to replace a 28cc crank - shoud I ever need to - might investigate that in the next week or so - not that I need to of course ).

I wonder if it would also work with the old DL50 bits. I have a couple of very low run time of the "Version one" of those (the one with the weak crankcase lugs) I might have a bit of a play also - like you, I have a few spare crankcases laying around that are not useful for anything else.