Hi, I have 4 chickens (Aracuna, Buff Orpington, Polish Crested & a Golden Sex Link) my question is how big of a coop do the actually need? Their chicken run is about 5 feet by 15 feet long. Currently I have the two older girls in a converted dog house (about 4x5x3) the two younger girls will be moving in soon and am curious how big of a coop do I really need? Can 4 of them fit comfortably in the dog house or should I make a larger coop. Any suggestions would be helpful.