Butch
Kinda picking the fly sh** out of the pepper.
The point is Manufacturers are not advertising Higher payload. They are offering specs. On their brochures you can find payload numbers, GVWR and Weight of truck. They provide all the information required.
If there are those that feel it is an effort to dupe the public well they need to remove the foil hats.
As to the OP Nice job calculating truck abilities and your camper weights.
I was a bit lazier and bought a F550 so I didn't have to calculate payload. Well not entirely true. Truck weighed 9000 lbs with a GVWR of 19500 lbs. That was the extent of my calculations.
I hate math :?