ORIGINAL: tailskid
... use the 'slab stab' and install it. Then 'build' your airfoiled stab on that piece.
What he said!
For a diamond airfoil, simply add a spanwise stick on top and bottom at about 25% of chord, then Monokote over the whole thing. Simple, light, behaves about the same as a curved airfoil. The Taurus and Orion models by Ed Kazmirski (circa 1962) used this technique. It still works. [8D]