Hello my dear FOUR BANGERS!

I'm currently flying my Saito 72 powered ship with a two blade 14"x 5.5" wood prop...everything runs perfectly well...
BUT!!! : in order to reduce the G.P. I am considering to try a 3 blade (wood or carbon...anything that I can get my hands on...)
What DIAMETER would be your first choice for a 3 blade prop for the Saito .72?
The ONLY 3 blade prop that I have right now is a Brian Eather CF 12,5" x 4" (that I can repitch to 5 or 5,5...) what do you think???
Thanks!
Claudio.