Dumb heat tape question

[Bighead]

In rack systems, the heat tape runs along the back wall, right?

I'm trying to figure out a bare-bones type rack system. I was thinking of basically just stacking the rubbermaids on top of each other to eliminate the need for seperate shelves. I know it won't be as convenient, but it will still work, right? There will still be walls around the top, bottom, back and both sides, just not in between. Am I missing something that will keep this from working? Thanks