My A&M's are set up at a 4:1 ratio. Some of my hens were a little bare when I got them, but since I have gone to this ratio, none of them have gotten any barer (is that a word?). The younger hens put in with these groups show no feather stripping at all. I will go to a five to one ratio when I increase my breeding numbers and retest fertility then. I would keep a few spare males just in case if you decide to go to a higher ratio. If you have a 3 or 4 to 1 ratio and lose a male you could just place each hen in another established breeding pen. However if you have a 5:1, you would probably want a replacement male for that pen.