You got it, man. It looks great. Smaller chamber for sure, but the Proma GP for the Puch cylinder is small as well and does great. I expect great low end and mid range for a stock cylinder.
I'm going to bolt it up see how it does and then shave the head and port the exhaust a bit. My buddy did this with a fatty 'burrito' pipe he fabbed and the bike did almost 50.