Can't believe this thread is still alive. I just put my old GMS .47 on a Spot On 50. The engine never did run very well. I drilled out the carb inlet and removed the remote needle valve and I am using an OS muffler. It is running pretty well now and it starts right up after it is warmed up. I needs a little more power though.

I am going to try a Vess 12x6 next flight. Wow that prop is light! My APC 11x6 is a little lacking - might need a bigger engine though for this plane.

The check valve looks like a good idea adji. I hate when it does that. I wish I would have thought of it when I was running little Norvels.