Material Used for Backing to Create Seats/Cushions

[Howler]

About two years ago, I created new seats for my boat, I used the existing plastic that was cracked/broken and deteriorating as patterns and cut some 1/8" plywood, painted that to use as a base. Fast forward two years that plywood didn't hold up very well. I'd like to try this again but need a better material as the solid base/backer of the seats/cushions. To make this a bit more interesting, one of the larger seats I need to create has a 90 radius over about 18" so the material I use will need to be flexible or at least formed.

Can anyone recommend a good material that can be used as the base of the cushions/seats that I could form for my curved seat and last for more then a couple of years?.

 

[Chris1956]

Flat seat bottoms or backs are usually 1/2" plywood. Seal them with polyurethane, before installation and use stainless steel staples.

For curved backs, a plastic is used. It looks to be about 3/16" thick and is held on by Garelick clips. Not sure where to get it, as I reused the original pieces from my SeaSwirl.

This plastic is used a lot on Seaswirl Striper boats. There is a website for SeaSwirl Striper boats where they likely know what it is and where to get it. Search for Stripers Owners Club (SOC).