You're not wrong, Muddy! And how many other hairbrained failures is he responsible for too? LOL One step forward, two steps back.
Before I installed it the first time, I ran a bolt through the nut and everything felt great. The cage had been weld repaired at some point in the past and although it didn't look particularly sound, I figured it had been good enough before, should be good enough now. Damned assumptions. Turns out the bolt wasn't the right bolt although I thought it was...just a size smaller I guess. When I found the right bolt, the fit was snug and applying a bit of pressure with the wrench was all it took to snap things off.
I didn't feel there was any other effective way to get in there and effect a reliable fix except to remove the freshly welded piece and do it properly. This time I ran a tap through the nut threads and made sure everything was good in that area. The existing cage was in rough condition, so I salvaged a nut cage from one of the scrap parts and tacked it into place. The welds are still lacking in beauty but should make up for it in effectiveness.
Welded the panel back in place but of course the gaps are wider now. Still need to grind and finish welding but I should be able to move forward now. Until the next hurdle tries to trip me, at least.