Jake,
I looked into this several years ago as a possible option for the bedwood in my 53. The main downside that I found was that all of these "plastic lumber" boards have a tendency to sag much more than wood if the supporting members (i.e. the joists in decks) are too far apart. For 5/4" decking (and for ADs the bed boards are 3/4"), the minimum joist spacing is 16" (
Trex Product & Installation Documentation ) The crossmembers in the ADs are much farther apart than this. Without installing additional support "joists" between the stock crossmembers, these "boards" will very quickly sag between the crossmembers.
By the way, if you use these plastic composites, there is no need to paint them. There are many manufacturers and the boards are available in several colors, including black.
We had another thread on this topic a couple of years back.
Bed Wood?
