We had a couple of 6” thick latex foam twin mattresses that weren’t being used and were in pretty good condition, and since I needed 39” wide cushions for the dinette benches in the 1956 Shasta, I decided to cut the ends off of the mattresses and use them as my cushion bases.
I cut the mattress fabric long enough to wrap the exposed end and slid a piece of ¼” plywood under the fabric and against the foam.
A few staples later, I was ready to start covering my cushions.
I put some thin batting over the cushions and stapled the seat covers to the plywood, too.
Back to the 1956 Shasta page: 1956 Shasta