I would love to have a 12" frame under my 320RS, but doing so would increase it's weight as well as it's price; both of which I can't afford. With an empty weight of around 11,000# and a GVWR of 14,000#, the current frame works fine. I don't plan on ever seeing anywhere near the 14,000# with mine, in fact, mine isn't even near 12,000# when loaded for travel. I've seen other 14,000# GVWR high line fivers with the same size frame as my 320RS and there still being towed down the highway in one piece!
I inspected the bare frames at the beginning of the assembly line while at both the Columbus plant and the Sabre plant. I was impressed with their construction and welded braces. They're even strong enough to support my M.I.L., which says a lot.
When I win Lotto and can buy a 3500, I would definitely consider a larger fiver, a Columbus, of course!
2013 Palomino Columbus 320RS
2007 Dodge RAM 2500 6.7 Cummins
Reese 15K manual slider
M.I.L. in Florida for good!!