I built the LT kit and installed the .46Fx about 2 years ago. I also went thru the wondering about the best prop. It won't make an appreciable or detectable difference to you one way or tuther. I even ran mine with a .32Fx and could not see much difference in training ability. Page 14 of the owners manual says to use 10.5 x 6 or 11x6,7, or 8 on low end and 12x7 up to 12x9 forf sport flying and 11x7,8 or 9 for acrobatic work. I like the 11x6 for instructing purposes or general flying but any will work. You don't need the 5 pitch props for anything with the LT unless you are pulling gliders into the air.