Yeah, it’s hard with some of the bigger engines. I found out a piston and liner from a Tiger Shark .52 fits in a Super Tigre G51 flawlessly. The ports just need a little work to line up correctly, but the engine runs just as well as the original ringed version did despite being a true .46 now instead of a .51 or .52. It just takes some messing around with parts from a few engines to find something that could work.