Use a razor plane and put a 35-40 deg angle on both the control surface, and it's associated "wing". This will give you a 70-80 deg total deflection when you hinge them, (If you get a perfect gap) and maybe a little more in reality. This is way more than enough for 3D, and will actually probably be more than your servos are capable of moving, unless you have really long arms/horns and high torque servos.