Interesting subject,I'm new to this forum, but may open a new can of worms,I build motorcycle dragrace engines, from complete cylinder heads ,extensive porting,flow testing, seat and guide installation serdi valve jobs etc.4- cycle but anyway ,Knowing what I know about piston port 2-cycle engines ,I have a question? When you mill a cylinder head to make the combustion chamber smaller you raise C.R (compression ratio),correct? when you remove material from a cylinderhead chamber it increases c.c's lowering C.R correct? Then what happens when you remove a moderate amount of material from the lower end,Crankshaft, cylinder sleeve, cases piston skirt,etc. ? My point being, My take on piston port 2-cycle engines whether it's nitro or gas, Their are primary and secondary compressions going on ,again I am just asking a question , and not trying to stir the pot, actually it's a three stroke, think about it,When the piston travel's upward and the crank window opens and its drawing in fresh fuel charge on the compression stroke , when the fuel ignites driving the piston down on the power stroke it also exausts and uncovers the transfers to allow the fresh charge into the c.c (Combustion chamber) from the crank case performing three actions in one revolution , so my question being ,By removing material from the lower end any at all seems to me it would make the secondary compression lazier on discharge through the transfers, in other words would compromise velocity, and make charge motion slooooower, and yes I know there are many variables, maybe these engines are allready to small in the lower half , where is the ellusive balance,Just My 2 cents. Thank's Mike R.