I just found the Sky Raider... looks like a typical trainer style aircraft. I would start with the 11X5... or maybe an 11X4 with the .40 engine.

Which engine? The .40 LA or weaker end of the line .40 ci engines (most bushing bearing ones), I would use the 11X4. The TT Pro 40 or high power end of the .40's (most ball bearing ones) I'd use the 11X5.