The following is kinda crazy silly, but I've done worse before.
I added up how much extra you could add to the dry weight of the Windsport 35M with 4 holding tanks
80 Gal gas 480#. 208 Gal fresh water and full waste tanks 1,734#. 88# propane. Family of 6 900#. 500 # for towing that Jeep on a dolly. That adds up to 3702# wet.
Now add clothes, food, chairs, BBQ grill, kitchen sink and on and on .....
As everyone always advises WEIGHT your rig. Weight can sneak up on you!