Correct that is not my truck. Here is my truck at about 350,000 miles.
Guy said he has towed that double rig twice avg mpg 13.85. Last trip Lake Tahoe NV area to Pismo Beach CA and back. Bet that lil EcoD got a good workout that trip as he had to cross some good grades.
Truck has a tune and an engine brake and a factory TBC. Said this scale slip was done earlier. After which he removed the tailgate and relocated the spare to behind the 5er which removed over 100 pounds from his truck. Still heck of a load for a 1500.
"The superglide hitch keeps the nose of the trailer close to the cab until I make a corner so it helps with the wind drag of the huge fiberglass brick I have back there. With the higher pressure in the tires and the short sidewalls they help to make it more stable also. The weight of the fifth wheel is somewhat ahead of the rear axle also to not only does it put downforce on the front axle but also any side force is ahead of the rear axle to help eliminate sway in the curves."
rwrueter, Controlling a load this size in in-climate weather & road conditions is a legit concern. Especially run away or controlling speed down a grade and or emergency stopping a load that is over CVWR. I will say having the factory trailer brake controller and a turbo brake from a tune as this fellow has as does my truck is a benefit of having the little diesel.
As mentioned earlier heaviest CVW I have towed is 15,800. I have taken that over longer 6 percent grades. Coming down I have no trouble setting my cruise control descent speed and keeping it there with no input from my foot IE truck brakes just the turbo & transmission brake combo and the TBC. This keeps the truck brakes cool in case I am in need of an emergency stop. My original brakes went 293k and I am still on my second set at nearly 440k. (truck tows commercially) So the towing doesn't seem to prematurely wear the brakes.
Emergency stop with up to the 15,800 I have worked with has been very respectable but I was working with a new trailer with good brakes and my gain maximized. Emergency stopping the CVW of the 18,100 he was towing I can't speak to but I am confident to the rated max of 4th gen 1500 platform which is 15,950.