What you have shown should work fine. You can make your own horns out of 1/8 inch aircraft grade plywood (use ball links for best results) and get by nicely. Do take out most if not all the dihedral though or your ailerons will be very ineffective. I've made several with absolutely no dihedral (as long as ailerons are added) and they flew much better than the stock units. Even then you may need to couple in some rudder on turns to make them look right. Use two servos, one in each wing.