I used to tow a 'caravan' when we lived in the UK years ago. There was never any consideration about weights and regulations back then. I installed a tow kit to the back of my 1990 Vauxhall Carlton 2.0l GLS, hooked up the caravan and never even considered the weight distribution. The caravans were much lighter than North American trailers. I remember pushing it by hand to get it into the right spot if I couldn't get it in there by reversing it. I had never seen a caravan with slides until we emigrated and as for 5th Wheels, they didn't exist. Even now they aren't too common I understand. Even a motor home was at best only the equivalent of a very small class B or C. Not sure how anyone would cope with a 40' 5er although I have wondered if I ever moved back it would be nice to take mine together with the F350. There just wouldn't be anywhere to take it. Nowhere is equipped for full hook ups as far as I know.
Richard & Diane
2014 Cedar Creek 38FL
2016 F350 Lariat CC DRW
Retired Metropolitan Police (UK)