Had 3 Carriage 5th wheels with rear kitchens and still have one of them and NOTHING has ever moved at all or broken including thin stemmed wine glasses in the across the rear upper cupboards. "E" range tires at 80 psi always but of course, Carriage always has had rear shocks on all their 5th wheels and TT's on all axles.
A few years ago we were traveling along with some friends who had a 34' Bounder MH on a 2 lane road and their engine quit and barely got the rig driver side even with the paved road as there was a ditch nest to the road. Rather than the wife and their 3 kids sitting along side the busy highway as dangerous as that can be, they along with my wife sat in our carriage 5th wheel and the hubby locked up the MH with the flashers going and got in our truck with me and our dog for going to town about 47 miles away. He'd called on his cell to make sure they had the things needed to fix it and drove back again as he's an automotive repair person for his work and knew just what he needed.
The 2 wives commented that wow! the ride was really smooth and quiet and as good as riding in a car and no sway at all and could talk like if they were just sitting at the dining room table at home. The MH wife said it was so much smoother and quieter than in their MH and it wasn't a very smooth road either as it needed re-surfing badly. I personally have never ridden in the 5th wheel and was curious and we had had MU's ourselves.
Proper suspension with adequate shocks makes a huge difference!