Need help with dimensions for rat racks

I live in Canada, and have been unable to find cement mixing tubs.

I want to build a 3 tub high by 2 tub rat rack.

The tub I've picked is 16.9x34x13.7

How would I go about figuring out the dimensions and supplies needed?!

I'm not good with carpentry at all. My dad will be actually building the rack for me.

I'd buy a rack, but a 4 tub rack here starts at 250!!

13.7 Inches seems kind of tall to me. Can you post a link to the tubs you're planning on using?

I can't find it online. It's a 15q.

http://img.tapatalk.com/d15b6bb9-86a0-5346.jpg

I'm having trouble finding anything with the same dimensions that everyone else uses.

Everything else at walmart was way deeper. And I can't find non-curved litter boxes :(

So here's a few more questions:

If I do two tubs per row, would I just use one screen frame per level or would I make 1 screen frame per tub?

How much space should be between each level?

Do I want the tub flush with the frame? (I understand people use a cd as a spacer, but usually it's for a snake rack)

That tub is definitely not the dimensions you have listed. Take some measurements with a measuring tape and I'll give the the cuts. And one screen frame is perfectly fine.

Darn it. I picked a different tub then I wrote ahaha. I posted this hurriedly while I was in walmart xD

16.9 x 13.4 x 5.4

Anyone?