[JesseK]

Hmm, this is in deed much better than the last design. For further refinement, you could turn the bolt around so it faces the opposite way, screwing into a nut that's spot-welded to the frame or an immovable delrin block. Flatten the round shaft on the bolt at one point to give 2 or 4 flat surfaces for a wrench and I think it's nearing perfection.

It's still fantastic as-is though.