So I'm working on a coop for the ducks. They should start laying in a month or so. I have 9 female Welsh Harlequins. I would like to fashion the nest box with its back to a wall that I can open a door in the back and remove the eggs without entering the coop. How big should such a box be for 9 hens? I was assuming it would be one big communal box. True? How high should it be? I assume it needs a lip to keep the bedding in? How wide? Thanks.