Hello George I have a Mammoth on the Flyeagle F-15 and weights 62 lbs it originally had a Rhyno and would fly it but needed lost of runway and with the Mammoth now its amazing how it flyes.I have over 10 hrs of running time on the engine and I have not had a single issue with it and power wise its amamzing at the verticle on my plane I cannot say how satisfied I am with this engine.