I think the Trex would work great. I work with this stuff alot. The steel strips between the boards acts as a stiffener so I don't think sagging would be a problem. The stuff scratches fairly easily though. So it depends on what you feel is acceptable. You can paint it, but that defeats the purpose of having a "no maintenance deck". It will fade a little over about a 3 month period in the sun. But after that it looks great.
