The other piston was installed correctly. The ring ends on the damaged side both appear the same, with a small notch cut out on each end for the pin. I can get a picture tonight. I don't see how the ring could have turned itself around once the cylinders were dropped onto it.

I'm also noticing that the pistons are the old style JS550 single ring pistons, while I have a reed intake installed. Is that going to cause problems if I install new single ring pistons? Should I go to the double ring ones?