We tow a 32' TT toyhauler with ours, at a bit over 10K# when loaded with toys and water, it handles it well, although I wouldn't want to go much heavier as towing comfort will spiral down to where I would have much disdain even hitching her up.
Our Chevy Silverado HD2500 with over 3.2K# of payload capacity (label on door frame) has plenty of power, and we don't mind letting her rev up into the power band. Still a 12K# 5er would be more than I would take on, especially here in the mountain west.
Virtually every where we go we are at high elevation detracting approx. 3% of engine power for every 1K' elevation, we average 20% derated engine performance making it all that more difficult, anything more than 12K# would certainly hasten wear and tear.
We did think about going with a 5er when shopping a couple of years go, and we did find some nice light 5ers to fit the bill that were 10K-11K gvwr, we don't shop by so called dryweights, particularly when a gasser tow vehicle is involved.
My DW prefers flat floorplans so we decided to keep TT toyhauler for RV adventures that lead us off road, and purchased a used class A more suited for couples living and extended stays. Our Silverado is in good condition, getting a heavier 5er would require getting a new truck sooner than later.
