According to tower, max HP is gained at 16,000 RPM on the .46 AX. If you prop it so that the max RPM is 10,000--you are severly overworking that engine, and you are going to have heat issues and loss of useable life on that engine. Prop it so that you can get at least close to 15,000 RPM, if not the full 16,000. I'd imagine that engine could turn an 11x6 at close to 15,000 RPM once tuned properly. Then, if you only want to run it at 10,000 RPM, use throttle management. This will make life much easier on you engine, and your investment will last much longer.