So I know 2strokestuffing guy had issues with his in which he solved by basically running a regular ring with a vertical locating pin to keep it retained over a 100% of bore exhaust port. Limits the bulging (another novel idea).
It would be interesting to see how well these actually work. Low compression is the problem Alex ran into it seems with this design.
There is a patent on it so I imagine that makes it harder to get some?
After you thread the head on the piston you insert a retaining pin to keep it from unthreading.