OK so tonight I built up my new DMP aluminum stuffed crank with new bearings and seals, and installed it alone in the cases with the Airsal 72cc top end to check clearances. The vendor sent me two base gaskets, so I installed them both. You can see that the crown of the piston still sticks out past the cylinder, and the piston does not clear the whole exhaust port.
So, I think that tomorrow I have to order the 1mm spacer from Treats ( https://www.treatland.tv/MLM-puch-metal-base-plate-spacer-for-p/mlm-puch-metal-plate-oversize.htm?1=1&CartID=0 ) and use a paper gasket on each side of it. That should put the clearances in the safe zone. With that out of the way, I can figure out how to port the cases to match the cylinder!