I agree that the mice trays are a bit narrow for nursing (9 1/2 x 21 1/2 x 3 1/2). The tubs that I use in my mice racks are 15 1/2 x 18 1/2 x 4. Do you think this will be appropriate? They are the same footprint as the Van Ness tubs, (and both will fit my current racks) but not as deep. I can get these locally for $3 each and have no idea where to get the van ness ones without paying shipping.

I guess you're right about the concrete tubs being the way to go. I only have 1.3 in my concrete tubs, but I feel 1.5 would still be fine, however 1.5 in a jumbo litter pan would be a little cramped.

Ok, so lets assume the litter pans I'm currently using are sufficient for birthing/nursing single moms, and the concrete ones are what I will use for breeding, weaning and holding extra moms. It works out well to have the litter pan racks 8 high x 3 wide (24 tubs), which will be room for 24 moms to give birth and nurse up to weaning. The concrete tubs 1 wide x 7 tall (7 tubs) will give me 7 male and 35 female breeders. Then 1 more concrete rack would give me 7 tubs to use for weaners, hold backs, and extra moms. Does this seem like it will produce over enough to fill my needs? Is this what you would do or should I have more or less of something?