Do one of these, a Zagnutz made out of fan fold foam. 48 inch span, cheap speed 400 motor and run a 5.5x4 MAS prop on 8 cells.
All ya need are two HS-81 servos, one for each elevon. The one I have here is a ducted fan model I call the "Fan Nutz". It flies pretty slow though but I get alot of flight time off of the 3 cell lipo batts.

Dave...