I've tried several, but am still searching for the optimal. My 3.2 is installed in a Lanier CAP. The best prop so far is a wooden Zinger 22x8---but it seems kinda noisy. I've been experimenting with a Menzlik 21x10 which is very quiet. However, it doesn't seem to slow the plane down as well as the 22x8. I think a lot of this depends on the airframe----i.e., drag.