Wow, sucks hard. Are you going to get the replacement piston from Treats?
I tuned/broke in my Parma 70 at Bomb Prom. My setup is odd... very rich:
AV7 Parmakit 70
Two base gaskets (1.6mm thickness total)
Stock AV7 Head
Beer Can Gasket (leaky, leaving today)
Doppler Endurance Crank
102 Main (!)
Malossi Red Filter
It is still not tuned right but I got color on the plug on a very careful plug chop (all WOT) and then proceeded to blast, big time, for 50 miles. I'll tear it down today and look it over but it felt very strong. I can't actually get WOT unless I roll it on slowly as it picks up speed. Plug chop was done this way too.