Right now I've got a tub with three nursing moms, more than 30 babies, and they're all doing fine in a giant pile in the middle.
The thing is, the female mice all have to be housed together from the beginning of the pregnancy in order for them not to eat the babies, in my experience.
Just 0.1 normal BP, 1.0 mojave, 0.1 California King, 0.1 Saharan sand boa, ~20 hermit crabs, a Patriot crab, 5.0 rats, and a herd of mice and ASFs
I use small tubs (14x12x6) so I always keep 1.2 in the tubs. As soon as the babies reach 3-4 weeks old or I see pinks in te tub I take out the babies and put them in the grow up tubs.
This way I ALWAYS have breeders set up. I never remove males and only disturb them to clean. Seeing as there in a rack feeding and water is all done from outside the tub :-).