I just stack and wedge the seat cushions on the bed before travel, between the back wall of the hull and the counter. It takes a minute, and they don't wind up on the floor.
Our cushions are fabric on both sides, my friend's Casita
cushions have vinyl on one side. Hers are held in place with velcro dots attached to the seat and the vinyl portion of the cushion. I use shelf-liner from Ikea (bumpy, plastic stuff in a roll) and a non-latex shelf liner from Lowes to keep the seat cushions from "scooting" while sitting, and in the drawers of our trailer.
I don't know how it lasts out west, but in Florida's heat and humidity, the shelf liners with latex can down after awhile, and leave a pattern on surfaces, so I don't use them anymore. (Had a lot of fun removing the residue from a rug liner from my ceramic tile floor in the house.)