I have NZL’s and my nest box is 10”x10”x10”. So far it has been worked well for the 6-kit litter. I have metal hanging cages and attached the hanging wire nestbox below a hole I made in the floor of an unused cage. The setup is three adjoining bays with dividers. When not pregnant, the mamma has the left bay, the buck has the far right bay, and the middle bay is empty. The week before kindling, I removed the wire divider between the dow and the empty bay. Although the nest box is all wire, we cut a piece
Of 1/4” plywood for the bottom. It seems to be working well, although this is our first time having a litter and using this system.