IMHO verify the VEHICLE tongue weight rating. If it really is 575# (I think it is, because they removed the frame on those, right?) and you agree that 13% is the minimum tongue weight of FULLY LOADED TT, then the max FULLY LOADED TT weight is 4,423#. This would be a popup I think.
Note putting a Class 5 receiver on a Pinto would NOT increase its tow rating.
We have towed over 100,000 miles with an ML320 which had a frame, and loved it. When we wanted a new Mercedes (old one had over 200,000 miles total) we drove to our dealer to buy a new one. Low and behold NONE of the new ones could even tow as much as our 1999 ML320. In fact no where near as much. Dealer even called Mercedes to verify strange ratings, and was told that was it. Not meant for serious towing. We bought a Ford Expedition.
