I watched the ys flyers at the nats and this last weekend at one of our local contests. I'm impressed by these motors. Being as they were parked beside me in the pits got to talking with a couple of them and their setups. 170's on glow. One guy was running an 18x10 on wildcat 4 stroke fuel. Thought it was a little under propped, but the power in the air was amazing. Other guy was running 30% cool power. Looked to be easy starting and the vibrations at idle looked good.