I bought one of these last month. It has now been retro-fitted to be a coop and a run has been added (10'x6'). The last thing I need to add is a roost. My question is this: How much head room do my chickens (Barred Rocks) need once they are full grown? They are only 11 days old right now, but we're getting everything ready! I'm so excited!!! Thanks, guys!