RE: engine porting
Liner and shaft timing are somewhat important, but look at what you can do at BDC to unshroud the boost ports. If you take notice, the piston skirt on most engines interferes with the easy transfer of gas at BDC. The trailing section of the cranks' counter weight can also be dished to assist flow into the forward boost port, this also helps smooth out the engine after you've notched the piston skirt and oval sectioned the rod. Another tip that has nothing to do with porting but will increase pumping action [volumetric efficiency] is to go with a Cyclon style backplate to decrease crankcase volume.