Lots of guys do it. I wouldn't. Forget payload ratings- you'll cross the rear axle rating by a LOT before you even get in the truck and that is just a problem waiting to happen.
I am maybe a bit old school in this thinking, but 5th wheels have no business on half tons. Even the coveted F150 HD. It's still a half ton no matter what the brochure says.
The dude pulling one with a Taco? He's not right in the head. Must have been born under power lines or something. I encountered a family in Cypress last year who had a cougar 5th hooked up to their '13 Longhorn 1500. Said it pulled great and felt really good. I know the ratings on these trucks. I could guess pretty closely that with that 5er, a family of five, plus hitch he was likely 1500 to 2000lbs over his GVWR and a good 8-900lbs over his rear axle. I imagine it will pull just fine- right up until one of his axle shafts ejects itself on the highway.
Probably only a few instances on here, but head to RV.net and search there. You'll find plenty of F150 and Tundra guys that think their half tons are sprinkled with some kind of magical "almost a one ton" dust and do it all the time.
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