I have A GWS 300 Slow Stick that I have recently had upgraded to a brushless outrunner motor. The Problem that I am having is that the new mount & gears that I have to use for the brushless motor, the shaft that it drives it doesn't have any thread on it like the stock motor did. What i have done is bought a prop save (Basically the same as in the picture below) However when I have attached the propsaver onto the shaft and get the motor going at about 3/4 open, the bolts holding the propsave in place start to slip because the shaft it is attached to is spinning so fast. Does Anyone know of a good way to better secure the propsaver onto the shaft to stop it slipping?

Thanks