All jokes aside.... I've actually been in rv parks multiple times where guys come in with a half ton truck and a fifth wheel. My curiosity got the best of me one time so I approached the neighbor to check out his setup.
2017-18ish F150, Crew Cab, 4wd Lariat. Pulling a Keystone Cougar "half-ton towable"fifth wheel. In the initial course of our conversation, he mentioned that my 3500 seemed a bit overkill for my fifth wheel. Mind you.... 2020 Coachmen Chaparral 392MBL. 43' long, 15,500 lbs loaded. Why not just use a 2500? Because it didn't have the payload. His answer.... just do what I did... Extra springs, airbags, etc... Make it tow more. I explained that adding all of those helpers doesn't make the truck tow more. It doesn't do anything to increase the weight the tires can handle, axles, brakes, cooling, etc... It's like getting a chihuahua on steroids where I could have just gotten a pit bull. He then asked if I ever had a problem with trans or engine cooling with my rig. Short answer... never. Not even towing up a 7% grade for miles. He was finding times where he would have to get out of the throttle because the truck was getting hot. Imagine that.
We sat around and chatted for quite the while and came back to the payload on his truck. "The RV salesman told me that I could tow this rig with ANY half ton pickup." I told him quite simply, salesmen lie. "But... the payload on my truck is 2,100 lbs. The hitch weight of my camper is 1,500 lbs, so I'm all good."
OP - take this example into serious consideration.
He thought he was within payload. So I took him to his door sticker. Actual payload on his door sticker was 1,684 lbs.
"But.... Ford says max payload is 2,100 lbs." MAX payload on a single cab, 2wd F150 XL was 2,100 lbs with the max tow package and one 150 lb passenger.
We proceeded to do some real math. He had his wife, his son, and their dog with them.
Dad - ~200 lbs (-150 lb for driver, so 50 lbs)
Mom - ~130 lbs
Son - ~130 lbs
Dog - ~30 lbs
Total passenger weight: 340 lbs
He was using a B&W slider hitch - 287 lbs (used to have the same one)
He had to get the B&W Gooseneck prep kit installed - 141 lbs
Remember that original payload number? 1684 lbs? Considering the weight of everything mentioned above, his available payload was 916 lbs BEFORE ever hooking to the rig. This rig was loaded to the hilt, so I would almost guarantee that he was overweight on the camper (but no way to tell in the park).
At a minimum he was almost 800 lbs overloaded. The truck just didn't have what he needed. But... the salesman told him he could do it so in his mind, there was no need to check for himself. In fairness, I learned this lesson the hard way myself once. It only took once.