Locate dead center of each hole for the mach-catch. Go down 0.6150" and drill a 1/8" hole on each side (but absolutely no larger than 1/8"). Once the flat is rolled, you will need a custom-made bushing for the paddle. Install the paddle using the bushing and 1/8" O.D. rod. TIG weld the ends of the rod to the receiver and grind smooth. Then mount your shelf.