The big problem I found was expansion and contraction rate with plastic based materials. If you have ever seen a Trex deck on a very hot day after being installed in early spring without allowances for expansion, and you would know what I mean.
The Coosa board I have talked about in earlier postings is enert and stable. It will not cause problems due to temp or moisture.
The link below will put you in contact with a marina/boat shop in Meaford that regularly ships in Coosa from Nova Scotia. The shop didn't even charge me shipping on the sheets as they just tacked on my order of Coosa onto their own. Seriously it is the only way to go with no headaches.
Cliff Richardson Boats Ltd.