I haven't yet, but I will when I get new bed strips from Mar-K. None of the holes in the cross sills will line up with the edges of the 1x6 boards so I will have to drill new holes 32 of them if I count right. The Trex is about 7/8" to 1" thick depending on which one you measure so that is the reason for the 1/4" dado on the undersides. I would guess if you had a planer you could plane them to the required 3/4" thickness. Here are a couple of cramped quarters shots.
trex1 trex2
