I want to run E track to hook 2x4 hangers into and then create my bed. I've read a few posts about E track but they wander off to L track discussions. The E track is like 5" wide (high) so I'm not sure how I would attached to ribs that run horizontally at waist height as they would be wider than the ribs. Have found a few tantalizing photos of E track installed in Promasters but can't get zoom in for enough detail to understand how it's done. Anybody done it or have any advice? If I just attached it to 1/2" ply lining would it be secure enough or would it still have to be secured to the ribs also, through the ply? In trailer builds I have seen E track attached to the ply which looks totally straightforward, but I don't know if that's a thicker ply or if all/some of the bolts go through to ribs on the other side.