A simple way to remember how to prop. Start with the reccomended prop in the manual. Diameter= power, Pitch=speed. If you need more verticle or pulling power. Drop 1 pitch and go up 1 diameter. To go faster drop 1 diameter and go up 1 pitch. Example 11-6 is the base reccomended. Power prop would be a 12-5, speed prop 10-7. And so on. You do have the right idea. Get a bunch of sizes and brands. Do a little experimenting. Find something you like and stick with it. Also remember the higher you are above sea level the bigger diameter you will need. Simply because of the thinner air. Good luck with your engine.

Mark Shuman