The OEM bar is actually a tube. I used a Ram u-bolt mount and wound up crimping the tube. I had thought that measuring the inside diameter of the tube and then pushing a suitably sized rod through it would be a good idea, but I never followed through with it. You could have someone tack-weld the ends of the rod, or maybe use a piece of threaded rod and loc-tite a nut on either end.
Inside diameter is 3/8", outside diameter is 1/2". I would definitely try to beef it up before clamping anything to it.