The rails for the lid are pretty narrow, but when I glued them up (using Weld-On 4), they were quite solid.

The main thing I changed on the lid was the lip on the end to provide grip. The original design has the lip extended out slightly from the sides of the lid (sort of wings), which is fragile. My first version of the box had one of the wings break off when I dropped it. The wings are just to fill the space on the box, so I added the space back on the box side and removed the wings. Now the lip is the same width as the rest of the lid, so it’s much less likely to break (or scratch somebody).

I made two other minor modifications: I rounded the corners of the lid very slightly so that you don’t have to align it exactly right when you start to slide it in. And on the underside of the lip, I slightly extended one of the tabs downward. This makes it so that when you close the box, there’s some slight pressure, keeping the lid closed (and giving a nice satisfying click when you close it).