I have read some of the posts on here about the difference in the prop size and pitch and they were very helpfull. I have a Megatech P-51 Mustang and it came with a 4 blade 8x8 prop. I was wanting to change to a 2 blade prop for improved efficeney. I have caught on very fast to the way to crash a plane and have yet to get a flight off that didn't result in a bent gear shaft and or a bent prop. I was wanting to change to a 2 blade in hopes of gaining airspeed faster because my plane likes to stall out. My question is what size prop should I use in a 2 blade model. The motor on the plane is a speed 380 or speed 400 one of the two. (I have seen both of these motors listed on this plane before and am not shure which I have.) If it makes a difference the wing span is around 3 ft. (Just to give you and idea of the size of the model.) If anyone can help me with this I would greatly appreciate it. I am about to the point to throw the bird in the trash and move to another hobby.