We are planning for 4 laying chickens this spring and building our first coop. The coop is 6'x 3.5' with 2 nest boxes hanging outside to maximize space. we will have a 5'x8' run both predator proof. Can I get away without locking the door at night and if so can I train the chickens to navigate a flexible, clear plastic doggie door? Is this enough room for 4 chickens?