Mods to the piston include sleeving the gudgeon pin position from 13/16" down to 0.709" (18mm) using bronze for the bushes and using a 600cc BMW Isetta pin. I have made a compression plate to fit under the barrel to sort out difference in piston gudgeon pin to piston crown height. I still have to machine the piston for the valve cutouts. Pesky stroke has slowed things up but all looks good for when I assemble the engine. Chris.