ORIGINAL: carrellh
Another prop that "might" be worth trying is a 13x4 APC Sport Prop
http://www3.towerhobbies.com/cgi-bin...?&I=LXFGV3&P=7
It may or may not work well for your combination, but, it's only about 5 bucks to give it a try.
As already noted, though, the "best" prop is the one that work the way YOU want. My opinion of "best" only applies to me.
A friend of mine is running this prop on his OS55 in a Profile. It seems perfect for his needs. Fast acceleration and good speed. Give it a try.