When I had a .91 on my chippy, the prop it liked best was the 13x6x10 wood prop. It pulled better than the 13x8 and the 14x6. I have hundreds of flights on my chipmunk.

It DOES have three servos on the wing. One for each aileron and a third for inboard flaps. It's a nice setup.

Chipmunk Picture

-Cheech