I made my own out of some 1"x2" x 1/8" tubing which is the same size a lot of the aftermarket ones are.I mocked up some 2"x2" ones and I didn't like the look of them hanging down.Only thing I can say is to make the seat supports as well as they strengthen the floorboards in that area and most designs call for a cut on opposite sides of the tube so that you can bend the connecters to match the offset of the factory frame.Instead of bending the connecters to the angles shown in the plans,make the two cuts on the opposite sides of the tube and bend the connecter to fit flat against your frame.Hold it in place and tack weld the angles and finish weld them elsewhere.The first one I made was exactly according to plans and it wouldn't fit flat on either side of my car.