Set the high speed needle with the nose of the model straight up. You should be able to pinch the fuel line and hear an RPM jump. You should creep up gradually on the correct setting from the rich end. While airborne, shut the engine down at the slightest hint of sagging and re-needle it. One of those JETT tanks would be money well spent. If your engine doesn't hold a compression seal for 5 seconds while cold at TDC, then you have already cooked it. The APC 9x6 is the workin' prop with that engine.