RE: RCGF Engines
goirish, IMHO. I tested props for thrust/rpm's and I beleive the three best are-16/10, 17/8, 18/8. For break-in 17/8. I personnally like Xoar, the mas has to much flex for me.
What type of plane, weight and how you want to fly it has a great deal to do with what prop you use as well.