and add to that:
TV mfg assume 10% tongue weight and around 20% pin weight
And the hitch weight needs to be added to the truck empty weight as well further reducing payload.
Then Trailer mfg typically design for 15% tongue weight and around 25% pin weight further upsetting the calculations.
So, it's pretty hard to be able to tow the max rated trailer even without anything else in the vehicle without going over GVWR and still be way under GCWR.
My duramax when loaded with typical bed stuff, firewood, firepit, cooler etc. along with a 9,000lb bumper pull with 1400lbs on the tongue and either 5 passengers, or my son and an additional motorcycle in the back is right at 10,000GVWR.
