You're probably asking the wrong people for advice here. I heard the same thing about my setup, AF 860 on a short bed Ram 2500.
And it's not unfounded, but if you are aware of the loads and plan accordingly then alot of risk is already mitigated.
Yes a 4500 series dually would carry it with ease and yes you'll be way over your gvw, but you already know all that.
I believe the AF 811 is just an updated 860, maybe a couple inches longer.
I had no problems on my maiden voyage last month, all the way up the Alcan Highway. Good test for the truck's suspension and wheels for sure!
I have Toyo MT's on mine. Again, not ideal for camper hauling. Tall, squirmy mud tires, siped to boot, but they are rated for 3950 lbs. Kept my tires at least within their load rating!
The OE GM PYO rims (16" aluminum wheels of that era) are very stout. Dont know the load rating but they will pack that camper without issue, based on my experience with my 02 DMax.