DUDE LOL
go weld ure crank first , then go get the cylinders ported...... Its not really about bore size when ure talkin miniscule cc gain..... ITS ALLLLLLLLLLL aBOUT FLOW !!!!!!!!!
Go spend ure life savings on a bad ass port job, a 4mm crank , and some nice domes and clutch. HANG ON
I have seen stock stroke / stock cyl bikes STOMP on 4 mill's , just because they have better porting/rider ?