As people are noting, different props give different amounts of performance. As a guide, the O.S. Max .46AX should be propped to turn in the mid-to-high-12,000's when leaned to just rich of peak RPM. If your prop will allow the engine to turn that RPM level AND fly the airplane in the manner you like, you have chosen the "correct" propeller. It doesn't matter what brand or size is on the prop. The bottom line is how the airplane flies. Da Rock had it right....what works the best IS the best, and you'll find people with the same airplane/engine combo using different props because of the way they like to fly the model. However, it's good to remember that the engine likes to turn up at full throttle, so work from there.