I use deep tubs rather than long and if i do a 1.4 or 1.5 the babies sometimes get trampled due to space issues.. I use a 1.3 now just because i feel its the max i can do. If you are using the long concrete tubs than 1.5 is great.
I use the one all the way to the left as a mouse rack, the one next to it for feeders or pregnant moms and all the others are 1.3