Here's a link and a diagram to ponder.

http://www.mh-aerotools.de/airfoils/hdipolar.htm

The diagram is pulled from Profili and shows what you're looking for in a good airfoil for your racing application. Note how the left side lines form sort of a sideways "bucket". THis is typically reffered to as the "drag bucket" or "minimum drag bucket". Note how the low drag actually extends down to a Cl of 0 and eve a little lower. Yet it promises to maintain a low coefficient of drag up to around a Cl = 0.8. This is an excellent performance and it shows you an airfoil that will have a consistently low drag over a wide range of flying attitudes found on a race course. The curves down around Cl=0 to Cl=.02 or so are representative of the model in level flight. THe CL=0.8 area is representative of the model under high G loads in a tight turn at high speeds.