Yeah, after reading this thread
as well, i'm swinging towards the SAT.
I've seen some of the overbuilt mounts people are using for Scorpions. I've got a friend who welds blast furnaces and heat treat furnaces for a living. He's a pretty skilled fabricator, has the tools and access to raw metal materials. Other than welding and brazing, i've got any tools necessary at my house.
Right now i'm thinking a design something like a miniaturized "5th wheel" or "gooseneck" hitch. Those hitches bolt through the bed into the frame itself. A particularly trick gooseneck hitch I saw actually sat underneath the bed, directly on the frame. You remove the bed, lay the hitch on the frame, cut a hole through the bottom of the bed and then bolt the bed back on, sandwiching the hitch. This particular one had a ball you could remove, flip and reinstall for a completely flat bed. Something like this http://www.popuphitch.com/flipover.htm
That would be pretty involved, but I could do something similar. An H or double-H on top of the bed that used the main bed bolts would be robust enough.
I've thought about losing use of the bed, and I have a solution for that. When camping, I can pack most of the stuff around the antenna. Or, if I have larger items, if using a Scorpion, the antenna could be on a quick disconnect. That still leaves a pin sticking up, so if I want to retain the ability to carry plywood or sheet rock (I do), i'll have to make the mount easy-ish to unbolt entirely.
I know there's no final radio purchase, technology will forever march onwards. I try to define uses for my purchases before I buy something. Otherwise i'd be destitute with a garage full of toys.