Sportstar back seat suggestions

[carlsonwa]

So I have this back seat which is one big cushion. When you step on it or sit on it, it basically has no structure. I am having some vinyl work done this winter, and would like to rebuild the rear seat to sit up on the ledges on each side of the boat and use a support under the center in the middle. The other seats utilize a thick plastic material. Would be nice to find a sheet of that material and build from that.

Here are a few photos of what I have. The current seat sits so low and I can't leave it there while towing or it would possibly fly out!











Any suggestions or pictures of your Sportstar/Prostar back seat would be great!!
Thanks