It was a Winnebago, I forget the model. 32' as I recall. This happened nearly 20 years ago, so forgive me for my lack of details.
The large rear overhang much like yours made it handle like dog ****. A little bit of control over the chassis as far as the seesaw effect would have helped a lot. When we crashed we had a trailer full of racing stuff, the trailer (home built, four wheel brakes) and contents all survived without issue. We still tow that trailer with our DSR to vintage races. The motorhome basically exploded. Not in a bomb type of way but rather an inertia type of way. My seat belt was attached as you described, to the seat itself. The drivers' seat had belts attached to the body. Not cool. My father is alive and well and still ****ing **** up, if you met him you'd understand what I mean. It's a compliment.
I will never forget picking up my wrist watch off the asphalt along with a box of cereal. A very odd situation that one. Try to balance that beast of yours out. You posted here because you are concerned. I urge you to continue down that path.
Trailer and DSR to prove I am not a dog on the internet;
https://i.imgur.com/47HdvaV.jpeg