From what I've read here, the rule is 2-3 chickens per nest box. However, most of the coops I've seen around here are for relatively small numbers of chickens (20 or less). We are planning to build a coop with a capacity of 35-40 layers. Do I really need between 12-20 nest boxes? What do those of you with 30+ chickens have for chicken to nest box ratios?