I had mentioned during the building of the .66 that the 27 mm FG 11 piston is 1 mm taller than the stock 62 piston . The increased compression, if it indeed is, has not been a problem. It has not offered to kickback when leaning to peak. Although being conscious of that I have been careful sneaking up to the peak. When going one click beyond the peak it slows without pre-ignition raring it's ugly head. The additional height is above the piston ring.
Wrist pin holding the pistons even