I think Paul ended up with 64.75mm, maybe 65. No matter what I won't risk reliability, so still measuring options at this point. I would really like to know the length of the 350/400F top end studs, or APE HD equivalents. I asked in the other section but no answer.
Boring for 62mm pistons must leave the bottom of the 650 sleeve taper wall thickness very thin, probably just 0.051"?