As promised, here are some pictures of seat decking, also known as deck pad, flex pad, and insulator pad. The large roll is called flex pad which is 1/2" thick and comes in 20" and 24" widths in rolls 35' long. The other white pad has heavy vinyl on one side and a soft padding on the other side. It is about 3/8" thick, and is tough as nails. I got it on a closeout from one of my suppliers, and it was extremely inexpensive. The gray stuff is 1/4" thick, is a lot lighter, and is made of re-bonded felt. It's O.K. , but I prefer either of the other two. There are other types of deck padding, but these are the only three I had around the shop. Any one of these would work. The gray pad would be perfect over a seat-a-lator, and the other two would be better over springs.
No one lives forever, the trick is creating something that will.