UPDATE:
I'm sure everyone is waiting with bated breath for the rest of the story and unfortunately the jury is still out.
Well another couple of months has gone by and we've been stuck at home with our busted truck and bed at a time of year when we would normally do at least two trips to the NorCal coast. The delay is due to the fact that the welding/body shop we are using in Woodland is booked to the gills with work and could not get us in until today 2/12. We had hoped to do a three week DV/Mojave trip starting Thursday but that's on hold too.
Anyway we were at the FWC shop in Woodland at 8am this morning to have the camper removed [gratis, thanks FWC] and the truck bed damage was significantly worse than expected with a lot of deformation of the sheet metal bed and sidewalls [see attached photos]. We took it to the welding shop and it was more work than they expected based on the underside photos I had shared with them earlier. They are currently coming up with a new estimate and I expect that it will take a few days to do the work rather than the one day I had anticipated. We've also ordered today a set of the front bolt Mule Expedition tie-down brackets as shown above in the thread and suggested by Stan at FWC upthread. If they work that should go a long way to solving the problem. However in talking to Mule they explained that they were specifically designed to work with the Ford aluminum truck bed frame and they did not know if it would work on our steel bed frame as they are designed to be no-drill, utilizing existing holes in the frame of the aluminum bed truck. So that solution may be out the window since no one, including me, is interested in drilling additional holes in our frame. Apparently no one has ever attempted this application with the Mule bracket product to their knowledge.
We are scheduled to have the camper re-installed on the truck next Wednesday at FWC. It will be either the Mule front brackets if the holes align the same and with standard FWC turnbuckle tie-downs in the rear or standard FWC tie-downs in all four corners. We are debating whether we should add additional plates top-side of the bed but it does not seem that would do much to restrict the heaving that created the cracking and deformation in the first place. The consensus is that we had hit a bump or whoop-de-do and the camper had tried to launch from the bed. I must admit that does occur on occasion but I'd always thought that the turnbuckles would fail first in that event.
It was also implied that we'd let the turnbuckles get too loose thereby allowing the heaving to occur or that I had over-tightened them. Most likely the latter since like I mentioned in the original post I'm pretty diligent at checking/maintaining the turnbuckles. Now I'm not sure what the proper amount of tightening is...
Again it behooves camper owners, if you've read this far, to occasionally check the status of the tie-downs from the underside of your truck bed,
To be continued...