I am doubling the size of my free range flock. I need to redo the roosting poles and need some help. I currently have a ladder type set up but want to go to a 2 or 3 pole (2 X 4's) set up. For 20 hens how long do they need to be and how high off the ground? Currently they have 4 ladder rungs and are as high as 4 feet from ground of coop floor. I am planning on putting in a poop hammock so the area under the roost rungs can be kept clean. These are a variety of standard sized birds.