Hatchling Rack

I am going to be building a hatchling rack soon and I have a few questions about what you guys do....
First, the rack I drew up is huge, way bigger than I will need at any given moment but I designed it to hold not only my hold backs every year but also to hold what I will be selling off. I work with corns, ratsnakes, boas, balls, small pythons (Children's and Spotted) and ETBs.
First question - Do any of you use just the cups to hold and feed the animals ( corns, kings and ratsnakes) prior to selling as the primary housing? (caveat) if so how do you heat them and "store" them?
The racks I drew up are 34'' w x 14'' d x 63'' t and hold 48 Iris MCBSS tubs on 12 shelves; the other is close to that but uses Sterilite 15 qt tubs.
I may just be cheap, but this seems like I got over zealous in my design. Any input to this?
I plan to heat it with 1 strip per shelf of 3" Flexwat plugged into a power strip that is plugged into a thermostat ( I haven't done the math on the wattage but I should be ok there).
I have gotten alot of help on this rack and I have even gotten the chance to build it twice over here in the sand box using 3/4' ply and 1/2'' ply.
(with out the tubs of course or the snakes...)
Let me know what you think, tear it up i can take it!

Just a something I have noticed while building the rack that we have now. We built it out of plywood and used sweaterbox sized sterilite tubs. However most sterilite tubs I have seen have a raise or depression on the sides where the tops would click on and because of this will not sit flat with the under side of the shelf above. This is not a big deal for yearling ball pythons but baby corn snakes would definatly escape.

Just something to think about.

Kelly,
I'm not trackin'. It's been a while since I bought tubs but the last time I saw them they were smooth around the top, at least the ones I was looking at were. Are you useing the lock-top kind for photos and what not? I could see where that come into play. For this rack I am going to use your every day good ol' shoe box. I do know that the Sterilite has "feet" on the bottom that gives them a bit of hight. I drew my rack up for either the Sterilite or the Isis boxes ( Isis are flat on the bottom) with only minor differences in hight.
Thanks for the heads up and I will keep an eye for the gap causeing tubs!
Thanks, Blue