I have had my bigs (7 weeks) and littles (3 weeks) in the same coop with the littles in a completely enclosed 'play pen' for over a week now. I haven't attempted to leave the littles' door open so everyone can mingle yet. There is a BIG size difference between the two flocks and I am not sure when to start making introductions. How closely will I have to watch? What are the first signs of aggression? I have read up on how to make a panic door but just because of the way the play pen is situated there is a real possibility of a little getting caught around the other side and having no way back in. I hatched these littles myself and a couple were VERY little (pullet eggs) so I am very mother hen-ish about them.