The matresses in our '79 20ft Minuet were rather flat. I was unable to get the upholstry zipper to work with out breaking. I am not handy at designing or sewing...So per a suggestion from here I bought a futon mayyress for the side couch/bed.
It is soft, comfy, a bit bulky but flexible. I only bought one cover for it, but plan on getting a few to swap off as the mood warrants. (Where did someone find a jungle cover? Any good sources?)
Structurally the bed/foldout is still fine. Sure, my matress doesn't match my end upholstry but at least I am getting a good nights sleep<S>
in a (Isn't it cute?) 1979 20 ft Minuet