rahawk, the GVWR is 22000. The published GCWR is 26000. Ford determines the weight ratios and the hitch capacity. As you can see, there is only 4000 pounds difference between the GVWR and GCWR. I think you would really have to load up the RV to max it to 22000. Considering the GCWR should be part of the equation as well, considering the suspension and braking systems.
Also, pulling a trailer will add tongue weight to the rear axle.
Just some thoughts,
Darrell