I agree OMPEdgeFLyer, I had a mvvs .49 on mine then went to a os .46fx and can still hover less than 1/2 throttle, a .40 fx would fly it fine as a matter of fact I'm putting .40fx on my SLEDGE. The SECRET is how to get the performance out of the motor, I use a Macs header and a .25 to .32 size Macs tuned pipe (smaller tuned pipe for more torque) which gives more back pressure allowing for lower idle and a huge low end power increase, and instant response from the throttle , no waiting for it to spool up the prop.