I was using a Scimitar 17x8, but after breaking the one I had, I had to switch to an 18x6 Powerpoint or a Graupner 15x8 3-blade. maybe I was overloading it. The scimitars seemed to not really load the engine all that much and wound up nicely. I have a 16x8 and some 17x8's coming. I'll try all the ideas above. While messing with the Graupner I did find it ran better running a little richer than I had it, but then I ran out of time.