Thanks for info Ed,I run in my 3rd SK 50 Last weekend.It has aTower muffler on it.With a 12-6 APC it screams.I couldnt tach it I dont have any.But It seemed 12-6 prop is less yet.I think it is Tower muffler s effect.On the second tank an advanced pilot friend of mine flew it in front of a World models Dago Red and flight was great as engine too.Im so happy to discover SK brand engines.I thank you especially with your comments to agree my pioneer support of SK brand engines.I hope to hear your SK 50 comments here too.