Adding hens to coop
That one hen is going to be stressed, but it will all sort itself out IF you manage the situation and they have enough space to figure out the pecking order without being crowded. I have a FAQ about this here: http://hencam.com/faq/introducing-new-hens/
In your case I just might try the technique of putting everyone in at night, so the first time that they see each other is in the morning. Sometimes they wake up and say, "oh, I must know you!" Because the majority of your hens will be new they won't have staked a claim yet to the territory you might have an easier time of it. Do the 5 know each other and are already a flock? Or, are they all individuals meeting for the first time? Anyway, don't freak out when there are squabbles, but if there's one highly aggressive hen, remove her until everyone else is fine, then return her. She won't be at the top anymore.