You could always go to Lowe's or a lumber yard and get 1/8 or 1/4 inch plywood and just glue it to the top. When I first built a rack I had the same problem so I went with 1/4 plywood and glued it up there. It was a little to big so I took a belt sander and went to work on it and everything actually turned out great. Hope you can figure it out because they're a pain to take apart.haha