Ok, we have a thread about upper combustion chamber shape but not one about the lower half of the engine and although this is not restricted to either glow or diesel two strokes Ifind this topic extremely interesting.

So to kick it off please view this link concerning the Cyclon PC6 combat engine and specifically the pic labeled "View from the rear," showing the most unusual crank web cut aways used to enhance gas flow at the expense of engine balancing. A lot of this can be done by someone handy with tools to a standard engine - if they dare!

http://www.clcombat.info/pcsix.html