Mike,
As usual, I go contrary to conventional wisdom. I am presently using only one OS LA46, on a Cardinal profile with 2 blade Zinger 12x5. Take off at 7900-8000 rpm, 62 foot lines, eye-to-eye, Powermaster 10/22. The down side of this set up is that it seems to need more fuel to fly the pattern than the high rpm type run. Flew this at KOI a few weeks ago.
My point is that the engine will take more prop load than some applications would indicate. One of the Master Airscrew 10x5 props might be a good place to start.
Cheers,
Jim