I don't worry too much about the pecking order if there is not a size/age difference. There should always be more than one when you are adding chickens. After the quarantine period is up, just put them in (or you can do it slowly, never had to do that myself). The pecking order is usually figured out within a week. I've never had any serious pecking except with my first four girls. They bullied the youngest bantie pretty badly. No blood was drawn, but I felt really horrible for her!