I can vouch for Joe at SW. I have an RCGF 15 that had issues. Joe helped me out.
I bought a Boeman ring for my DLE30. He included a note that Chinese engines need to have the crankcase disassembled and cleaned up. Especially the reed cage. I did that and my engine runs much better.
I also have a NGH 25. It looks to me to be a better engine.