Lots of folks with stuff like this are just using a flat plate. Deltas generate their lift differently from regular planforms. With sharply swept delta angles the vortex over the upper side is so strong that a flat plate is as good as a brand name airfoil. But this requires an angle that is much sharper than 90 degrees between the two leading edges. If it's 90 or less then you're probably better off with a proper airfoil.