Oddly enough, there appear to be no nuts at all on the long carriage bolts that connect my top rails to the bottom rails. They have apparently been held on there for 48 years by the opposing friction of the two counter-curved rails. On the other hand, last time I tried, I was only able to get two of the 18 carriage bolts out.
For the next try, it occurs to me that pounding on them with the punch and 3 lb sledge might have failed because the plastic cabin top flexed and absorbed the energy. So I may try instead to chain the top rail to the hydraulic floor jack. Which would probably be a destructive, can’t-go-back-now sort of affair.
Now... how to apply that much force in reverse to get them back on...
Entombing them in epoxy, though ghetto, is sounding better all the time...
The plasteak looks great though.
BTW, there is no corresponding inside rail for the last loop over the head. But there should be. I recently installed a grab rail on the bulkhead in there. Seems like an obvious need.