Breeding setup?

So I have an 18 tub rack that uses kitty litter pans. I'm brand new to breeding rats so how would you guys organize your rats? So x ammount of tubs for breeders, x ammount for grow outs, x ammount for nursing mothers. And how many females per tub with a male? Thanks, here is a picture for refference of tub sizes.

http://i.imgur.com/9r8iNrU.jpg

I do it 2 ways

I either run 1 male through 4 tubs leaving him in 2 weeks at the time, those tubs house 2 females each.


Or I setup tubs with males, rotate females, adding one female at the time each week and removing the one that is obviously pregnant, once the pregnant ones re pulled they go in individual birthing tubs where they stay with their litter until the litter is 7 days old, after that the females are placed 2 per tubs in a cat litter pan for communal nursing.


I prefer the second methods allows me to rotate more efficiently and have more females, it also cut down on the loss as female left together at all time including during birthing will fight over babies and when they are born until they are about 5 to 7 days their skin is very fragile which lead to losses.