would be the stack getting bumped over if it got too high since the base of one cube doesn't interlock with the top of another cube like some of larger black-bottomed cases do.

I used to put those Ballqube cases in tall CD towers with one in each of the top 7 shelves of the tower and one on top of the tower. When I bought 4 more towers for the new house I didn't have 28 more cases to put inside them. They were out of stock at the time, and even if they were in stock that many would have cost more than I wanted to spend.

I decided instead to order 4 acrylic sheets to cover the front of the towers and install them in a way they could easily be removed. Here's a (poor quality) photo of 3 of my 6 towers. Two of the Ballqubes are on top and the other is a custom case containing the green 300SL.