How to mount a flatbed camper?

I really like the pocket-style bolts that @IdaSHO designed for his camper (photos here). I believe he manufactured his own.

I've been searching for an existing aftermarket bracket like that with the durability to handle a heavy truck camper and coming up short. Any ideas from the community?

I like the idea of bolting over straps/tie-downs. It feels more secure. But I know it's hard to line up so I'm looking for something that will make that easier. As an alternative, I've considered adding "wings" or guides that would shift the camper into place as you back up into it.

On the topic of bolting: how do bolted-on truck campers keep water out? Is it simply a gravity thing (as in, water will just run off the bed and onto the ground), or are they sealed in some way?