RE: How does changing the prop length/pitch affect performance?
An 11 X 4 would very likely slow the plane down quite a bit, and allow for slower landing speed. It also won't over tax that engine, where an 11 X 6 or a 10 X 8 would. (The 10 X 8 would definitely result in higher top speed and landings assuming they didn't cause too high a drop in RPM.)
Dennis-