Rich, Glad to hear you are happy now with yours. 9100 sounds a little slow for a 17-6, as mine turned an 18-6 at 9250, but there are differences in props. Mine are the Master airscrew classics. I like them due to their durability. I would say that as long as you are over 9k, it should run very well in the air for you. This engine, in my opinion, runs like a strong 1.20, and should be propped as such. I'm a little disappointed in that, because I thought this engine was supposed to be very good at lugging big props, which would allow for a transition into giant scale. My Sukhoi flew fine on the 16-8. Had plenty of power, vertical performance, and good manners all around. The Sukhoi is very draggy, so it's not too fast, but it is faster than the F90 with the 18-6. I'm running 10% Powermaster in mine, and will be sticking with it. It's the best fuel I have run so far.