That's a good point Emily and exactly why I only allow one plastic tub sideways per shelf. I too tried to put two side by side and found that they overhang too much and to get two plastic tubs to fit on that rack dimension, they are simply too small too be of any real use other than maternity tubs. That's why I went with a combination of plastic tubs and glass tanks and keep the tanks low on the rack to keep it balanced weightwise.