I just received a OS 50 heli engine this morning after I get off the net putting her in. Pretty much same case as the OS 46 diameter wise. Few changed in the carb from the 46. I'm putting my header & tuned pipe on it as well. In a heli I saw 3 last week that performed quite a bit better than the OS 46. Should be good, but I have a lot of time i getting very little extra gaps at the ailerons while still getting complete throw. Double checked for any slop at the push rods to stop any flutter. Using the JR 4131's there should be no flutter. We'll see Sunday if weather permits..