Im looking at making a drop nest box for my dutch rabbits. What size and depth should they be? Should it be in the corner or middle of the cage? I heard it was good to make a trap door type thing on top so you can close it when it is not in use. Do I need to line it with something? How do you attach it? My rabbits are outside and have individual rooves for their cages so will the nest material blow out? Thanks!