One of things that I was worried about was making a box that was "stiff" enough to not cause problems with the track as it is being hoisted up. The track doesn't like to bend. I built a box that had plywood on both sides. It was 1/2" on top and 1/4" on bottom. Until I screwed and glued that 1/4" bottom sheet on, it was amazing just how flexible the box was.