I use trios of 1.2 and keep everyone together at all times with great results. I have had a few acts of cannibalism, but that was done by my older breeders who had worn out.

I will be switching to mostly rat breeding soon, tho, as I now have larger BPs and it's just easier to feed them one small rat rather than 3 large mice per feeding. I will be keeping one trio of mice, tho, for future hatchlings and picky eaters.