And the plot thickens... Not that I really know what I'm doing, I am under the assumption that the piston in this C was the original one. I read that Sachs thread several times before posting. It would be nice if someone had a verified C piston to measure and confirm. It was missing from that thread and in my search efforts everywhere else. I'm trying to put together this Balboa at as low a cost as possible, using up junk and free paint and epoxy primer. I will splurge on handlebars, a pipe, cables, and whatever bits needed to make it go.
If this piston performs horribly I still have another used piston to try from my A cylinder. I also have an absolutely miserable 505B lower end that could be built with the Puch cylinder and spacer if I wanted to continue the madness. But that of course would still cost a bit...