Yes that is Trex board… I turned them upside down for less surface contact and wow. The boat slides right off! The boat buckles I got on Amazon. On sale right now. Work perfect. The tabs I welded to bottom of plates allow it to flop either directly and be flush with c-channel of trailer. So no chance of contact.
How long on the trailer now and have you seen any buckling on them? I laid them on my back porch and had to put 12" centered joists under them to be safe. I'm pretty sure this is exactly what I'm gonna do with my trailer I'll start building this winter, (and maybe frame some steel support under them)?
About 1 month. And no buckling because I welded 3”x3” angle iron under them running parallel, full length and drilled and bolted every 18” with carriage bolts. When the bolt heads pull down in the Trex they seat in valleys nicely! Love it so far. My tie down time about non-existent and it stays glued to the trailer over those bumpy dirt roads.
