I had a 17 Ram SB 3500 with a 4000 lb payload and carried a Lance 865 with a wet wet below 3000 lbs. It was a good match and felt safe and solid, but I knew there was a big load back there.
I would Not want to carry a 4000 lb plus camper on a SB srw truck. Besides the heavier weight, it is much taller than my 865 adding a more unstable feel.
In the past, I carried a Lance 981 on a 03 Dodge DRW and the ride stability with a dually is incomparable.
My opinion is that an AF 811 belongs on a DRW.