My city ordinance only allows 4 hens so expansion is not an option for me. I have a tiny back yard and can only build a 3 foot deep coop along the fence (length is negotiable). I have read 10 sqft per bird for the run and 4 sqft for the coop. Is this best practice knowing I will not get more than 4 birds? Right now I have drawn up 24 sq ft for the run and another 16 for the coop. They might occasionally be free range but the majority of time will be in the run. No predators other than rats. I read all 4 birds can share the same nesting box, is this correct or should I have 2 boxes? Is there a preference between shingles or metal roofing?