We just went through the same thing here. I acquired a 5 week old Barred Rock roo from another family, and was concerned about making introductions with our little flock (2 BO, 2 Sex Links, and 2 Barred Rocks) all 4 weeks old. I put him in a large carrier, with food and water, and faced it towards the coop. We watched him for a couple of days, then put him in with the girls. There was some chasing and flapping, but within a few minutes, they all seemed to settle. It's been over a week now, and they are getting along very well. It seems no matter what, they work it out. Just keep an eye on them, and it will be fine.