Bryan Carr in Calgary likes the 10-5 MA 3-blade on his Magnum XLS .36. I have not tried one, but if it works on a .36, it won't work on a .46. You might try the higher pitch versions. I know of a .46LA that used a 12-6 MA 3-blade that was cut down to 11.5". I don't know if he did further rework or pitching, but it did work very well, flying a USA-1 that was over 60 oz. Can't recall the guy's surname. Wade, I think, was his given name. From Central Calif.
Here's what they currently have on the shelf:
http://masterairscrew.com/3-bladeseries.aspxSadly, the MA 3 blade props are pretty expensive for "shot in the dark" testing, at around $10 each. They can be re-carved, re-pitched, and sanded into something different, but duplication becomes a problem.
You might try Randy Aero's "Magic" (Mejzlik) 10 x 5.5 (?) 3 blade scimitar electric prop. Being CF, it's plenty strong and stiff for IC engines. Keith Varley uses one on his Stalker .51 powered Sawyer "Continental". Pitched down to 4.5" or 5", it should work fine on the .46LA.
Steve