one i think that has gotten lost along the way, outside of the pylon world is good solid metal motor mounts, bobs27 mentioned metal spinners, this is key too. the imbalance caused by plastic spinners and flimsy motor mounts cause rpm loss, the thing i tell guys looking for repeatable speed is that plastic spinner is hurting you, and it will disintegrate and possibly hurt you and others as well...there is a reason pylon racers use metal motor mounts.