I'm building a drawer glide tray/shelf that will let me pull out the whole lighting system from my canopy. I need some opinions on what material to build the shelf out of. It needs to be humidity and temperature resistant. I was thinking of using the white melamine they sell in Home Depot for shelves, but its particle board and only 3 sides are "sealed". would this absorb the moisture and swell/warp? how about spar varnish sealed plywood?