I think I would like to try the backplate modification and also polishing the exhaust port and or rising the port.
Can you explain the drilling the crank - and or pic
Polishing ports and transfer passages will achieve nothing.
Do not even think of drilling out the crankshaft. The crankshaft is hardened and a regular drill bit will not touch it. Should you ignore this advice and start drilling then do not break into the intake window. The drill bit will grab and probably shatter.
You will need proper tools for this type of work and to observe some basic safety rules.
Ed S