thank you ...my homer breed and mate out side the loft ... i let one pair go out at a time to mateI know we mention that a prefered nest box is 16" X 32" X 16" but if you don't have a space then you can provide whatever size you can accomodate your birds. The reason alot of us prefer to height to to be 16" is because it gives the pair room specially when the cock want to thread the hen, they have enough space and you can guarantee who is the father of the young birds. I don't know if you notice that sometimes when a pair is about to do it that the cocks always gets bothered by other cocks. So do what you can for the birds and maybe later you can build another loft where you can provide them bigger nest boxes. Also remember pigeon are good producer so plan accordingly or you will end up alot of birds then disease will visit your loft, remember don't over crowd your loft.