Interesting project..!
I can only hazard a guess how to approach a project like this because I've never owned a good running .020.
For the best chance of success with a 3,5 x 3 or a 3 x 3, I'd build it like C/L Speed plane.
Make the wing and everything else as small and skinny as possible.
This gives the engine / prop combo it's best opportunity to "come to the party" when you shift into high gear with less diameter and more pitch than what is considered normal.
I'd also expect to spend time with an Xacto knife scraping and shaping prop blades to eliminate excess material that is there more for safety factor than it is for performance.
After building the "most minimal" airplane and spending at least a certain amount of time to find the best working prop the limiting factor becomes how much air you can get into that engine and possibly even shaving the piston. Shaving the piston not only increases RPM, but it also moves up the "Red Line" for ball socket longevity.
I've never had a good .020 specimen to play with though, so this is just late Autumn bench race talk from deep in the woods......
Last edited by combatpigg; 11-20-2013 at 09:20 PM.