Why not just allow clipping the Diameter down say 1/4" it would save all the hassle of new props .Here in Aus in our F400 we use QM40 motors on FAI fuel and used to use the grey APC props but some using modified cheaper engines were fracturing blades so they opened up the props to anything made in carbon the times have droped about 10 seconds since and on the F3D course at the Aus champs one guy was doing 65 second times. Too fast I say.
Terry