I did something similar with one of my shelves. They are made of MDF and I simply cut a hole in one shelf, then put the box of rags over the hole. Presto!! Don't have a picture currently, and can't get one. Shelf has been removed from the garage and has not yet been put up in the new shop space downstairs. I can definitely see the advantage of your bracket, however. Since the box cannot move around, yours will stay put much better than mine.