In my experience most A and B class motor homes are only rated to tow 3500lbs. NO weight distributing hitches allowed.
This is because the coach manufacturer scabs has to extend factory frame, and the hitch receiver is installed on that extended section. They are not comfortable with accepting the liability for any more than 3500lbs, and that does not give me much confidence in going beyond those limits.
Heck the frame may be good for 10,000lbs for all we know, but are you willing to plunk $50,000+ down to test the theory? I'm not.
I have seen a few larger (30'-ish) older class A motorhomes pulling 8.5x24' enclosed utility trailers home from the track on race weekends over the years. Trailer has tandem 5200lb axles. Weight distribution hitch is in use. No apparent problems. Who knows what was done to those motorhomes, maybe nothing? Not sure if I would take that as blanket evidence proving that it's an okay thing to do, though. Come to think of it I haven't seen any of those rigs last summer, so maybe the answer is "no?"
