I know that there are those who say "a prescribed sq. ft. per bird" formula does not work. But, this is why I continue to throw out the recommendation of 4 s.f. in coop and 10 s.f. in run per bird: tighter spacing will eventually result in behavioral issues. It can also result in disease issues. It will make it difficult to provide adequate moisture elimination b/c you have more birds oozing moisture from lungs and other points in a confined space. Even providing the necessary ventilation in a small coop is almost impossible b/c it's impossible to have that ventilation without the birds being in the middle of the air flow. Add to that the increased difficulty of keeping an area clean when twice as much poo is being eliminated every day as the space was designed for. Then, there's the "social protocol" of the flock. When Alpha hen says "Get out of my way!" She's really saying, "Get out of my sight. Go far away, or I'm gonna rip your face off." The lower hens try to comply, but can only move 3' away. In a larger coop with a larger flock, you can have a bit closer spacing. A 100 s.f. coop could have more than 25 birds, b/c when alpha hen speaks, the lower girls can move 10' away, perhaps moving behind a hay bale, and that does satisfy the social protocol.