Here is a pretty good link for rat racks and birthing racks and alot of info! I used his ideas for the rat breeding rack but had to put my own twist on it and I made up my own birthing rack just lloking at a few and got my own ideas. Here are mine so you can see.

Here is my breeding rack minus 2 tubs due to lowes being out when I got my supplies. I used clays measurements but had to only make it 4 high and not 6 due to the ceiling height in my basement so I just added another 4 to the right side of the original 4.

This is the birthing rack I made all with my own measurements and what not. Made it only 2 shelves high but can always add shelves higher as needed and as the ceiling height will allow. But Clays birthing rack should suit you good for your larger scale operation.

I just started out 2 months ago and got my first litters starting last monday. I had all my females go within 7 days and got 50 babies from 5 moms and I have one prego yet. I have had a few that have died due to unknown reasons. I lost 4 babies total out of them 50. They weren't chewed on or anything I just found them all blue and not moving. Just thought I would show you my small setup. I started with three groups of 1.3 and am gonna raise a few females up to make a few more groups.