You might get more info if you also ask in the RCU "1/2 A" forum:
http://www.rcuniverse.com/forum/forumid_70/tt.htm
Tower Hobbies has a couple of ARFs that use .061 to .074 but nothing for .049
http://www2.towerhobbies.com/cgi-bin...93p?&C=ACD&P=0
SIG
www.sigmfg.com sells a few Neofun ARFs that recommend .049 to .061