Flatbed....rails? boards? keeping the camper centered...

Oops, waited too long between beginning my response, and actually posting it, lol.

Reality Check - I like that set up, and the basic idea of what I was thinking. I hadn't thought about just studding it and dropping it in though. I was stuck thinking about how I could secure the rails without having open threaded holes collecting crud/corroding or bolt heads sticking up when the camper wasn't on the bed. But just having open holes and dropping the rails in when needed? That makes perfect sense now.