Ok, gotta run but here is a sneak peak at some of my piston collection.
starting left to right:
top row
KZ650, KZ750 low dome, KZ750 high dome, 64mm??(CB350T??), 64.75(looks identical to the 64 in many ways, thinking it is a CB350T 3rd overbore piston set(s))
Middle row
std 550, cb750 auto piston W/ "Gentleman's Express" & 0.330 lift valve pockets, std 750 piston with same mods, std cb650 piston
Bottom row
cb650 piston modified to "Gentleman's Express" specs W/ clearance for 550 running a 650 cam, next as before but w/+2mm to the diameter where I started the 15 deg cut, third +4mm, fourth +6mm.
These are a set I have been waiting on someone willing to try them out, and recently found a racer looking for an overbore within the 5% of stock bore rule. These make it with room for a 60mm overbore later as well as having great potential for a high CR piston.
gotta run!
l8r