rhagfo wrote:
1" X1/16"" strap steel, bent in my vise. Held up with a couple 1/4" bolts.

So you just drilled the bolts right into the underframe? I took a look today and I have nothing to tie to on the non-drain side, so was considering just tying industrial zip ties around the steel beams that form the inside of the rear bumper and hanging the fence post holder from there. It would be nice to have it closer to the drain, but we just bought this a few months ago and I'm not sure I want to start drilling into the undercarriage of the RV until I know more about it.
Thanks for the responses folks. :)