I found the thread. Here is the hitch I built for my F550. I'll have to see if I have a finished picture. The flat work is 3/8". There is a plate 2" bigger than the hexagon shaped piece on top welded on the bottom. The thickness where the ball passes through is 1 1/8". It's never seemed to notice the loads it has carried. Also, the hitch clears the frame's flange by ~1/8-1/4", per design.