I figured smaller pitch would slow me down and smaller diameter would increase run time (and same me some broken props, Doh!)
I may have to raise her up a bit and run like a 13x4 or something.
Still learning but your advice is well received!
But the smaller diameter will speed up the rpm's. So you would be correct with the 13x4, personally, my favorite funfly prop for 40 size planes is the APC 12.25x3.75