The Carl Goldberg Jr. and Sr. falcons both have airfoils for the tail surface. I think it was more common back in the day. I do not now of any current kits that have airfoil shaped stabs. I have a jr. falcon Had it for years flies great. But the one thing I have noticed is all airfoil shaped Stabs are symmetrical. so I am sure they are set up at 0 degrees incidence.
If I remember right Goldberg plans said it was to enhance the performance of the elevator. I am not an engineer by no means but I could see where a flat bottom airfoil on a horizontal stab would make for uncontrollable flight, the only exception I can see is a free flight model that would fly straight and level, even then inducing a stall on the tail would result in the nose going up and stalling the wing. Maybe