Rack Question

So i went to menards and i saw some wood pretty great selection for pretty cheap least compared to home depot. Anyways before i start buying wood i need the measurments and all and i was on Royal Constrictors designs.com and i saw this: http://www.royalconstrictordesigns.c...ages-medium--3
Now he says 28 Qt tubs, but towards the bottom he says the common measures of, 22"x16"x6. but the 28 qt tubs at walmart are 23.12"L x 16.9"W x 6.38"H
so now would his design fit the measurments of walmarts 28qts? I really dont know much about building and measuring much with wood and i dont wanna buy alot and cut and find out its not right.

He was probably using the sterlite 28 qt tubs, those are about the measurements of my rack openings.

hmm so ill be fine buying walmarts 28 qts then?

Yes the sterlites without the locking lids

What would be the best way to have the heat tape with it, on the back?