I'm late to this thread, but did want to speak to the flatbed concept. My tow vehicle is a Chevy Duramax K3500 dually, cab and chassis with a Hillsboro aluminum flatbed with a recessed ball.
I don't use the typical fifth wheel hitch. I opted for the Andersen Ultimate hitch. It, too, is all aluminum (weighs maybe 30-35 pounds), but can absolutely stand up to the demands of my 20,000# gross 36' Teton Experience Liberty. I don't have my Teton grossed out, but I'm well above the empty weight of about 13,250#.
The Hillsboro flatbed is 8' wide and 10' long. Before I got it, I worried that I'd miss the convenience and security of a typical pickup bed, but that hasn't proven to be the case. With the jockey boxes under the flatbed, I can easily carry everything that I need to set up for towing.
I leave the Andersen hitch on the flatbed all the time, since there's so much room on it and rails everywhere to strap anything I carry down (so far). The visibility all around the flatbed is great, since the typical box sides aren't in the way.
If I'm parked for an extended length of time, I'll remove the Andersen hitch, but since it has to be torqued down precisely for correct setup, leaving it onboard is just too convenient. If someone who knew how it's attached wanted to steal it, of course, and had the tools to do so, that would be an $850 mistake I would deeply regret.
I, too, have towed over Monarch Pass with this rig and my one-ton Duramax has absolutely no issues doing so. It's a really good way to burn up diesel quickly, however.
TJ