There is a thread on this site about the Moki 1.35 used in a pattern ship. I think they said a 16 X 10 or maybe 16 x 11 worked great on 5% nitro. They ended the thread saying "why spend $600 on an engine?"

I have a Moki 1.35 on a 1/4 Edge that cranks an 18 x 8 prop on 5%. I had to go to 18 X 8 to keep it from whining like a 40 sized motor at high rpm. The engine is ultra reliable and so powerful that I probably only use 8 oz of fuel a flight (running at partial throttle). With the 18 x 8, the plane slows down so much that I now land with a little power.