Like chips, you can never have just one, or 4, or 20 balls!
Stacking will soon get old as your numbers increase, and the animals suffer as you will not take care of them as you'd like.
One man's opinion.
:LOL Thanks I don't plan on breeding too many, maybe 4 tubs tops for now, that's why I asked, why pay for a rack if I have so little to use it for. When I get up in the projects I will spring for a rack.