I don't know if this will help you, but I'll tell you what I do. I put my just-hatched chicks right in the coop with my bigs. They have a chicken-wire box that they stay in and they have their own pop door that goes to a little pen within the area that the bigs occupy. This way they can all see and be seen, but the littles cannot annoy the bigs and the bigs can't attack the littles. That's a big key for integration, they all should see and be seen so they can get used to being around each other
Then at the 2.5-to-3-week mark, I lift the pen so the littles can go out and explore, but they have a safe place to run back to when the bigs chase them.
Note the pen is elevated on 4x4s. The littles can scoot under to get back in the pen, but the bigs can't follow them.
Then, a week or two later. I elevate the box. Same deal, the littles can go out and explore, but can run back and scoot under the box.
When they seem like they're all getting along okay enough, I take away the pen and then take away the box for full integration.
You don't have "little' littles, but the same principles apply. Give them a space to see and be seen, but have avenues of escape because they will not be welcome into the flock right off the bat.
Thank you, aart. I consider that high praise coming from such a knowledgeable and long-standing forum member. In all honesty, though, I just took ideas that I got from others here on the forum (I'm sure one of them was you) and ran with it. So....thank you.
Did you notice the MHP in the top picture? It's a piece of wire shelving that I laced a heating pad to the bottom and covered it with a pillowcase (quite a bright, multi-colored case it was, too). Brooding chicks right in the coop starts integration right off the bat. I'll never do things the old ways again.