Evolution 18x6 wood prop is OK. My 1/4 scale CUB at 14.5 lbs I use a 17 X 8, 18 X 8 XOAR and an 18 X 10 . After break-in prop the engine to give better than 6800 RPM and you should have good performance. Keep a log of your RPM. You could break-in using the 18 X 6 and when the RPM increases use a 8 pitch prop.