My first experience integrating was tough. I put them for 7 weeks where they could see each other. Then when the chicks were 14 weeks, I put them in the coop at night. My first mistake was putting one of the cockerals in first. He freaked out and sounded his alarm, which woke everyone up. All but 1 of them did fine, but for 2 weeks there was a lot of chasing, bullying, pecking, etc. (no blood) One cockeral however, was pecked pretty badly on the top of his head.(blood) He had messed up toes, which caused him to be unable to roost. So he couldn't get away from them. I'd go out and find him in a corner with his head pushed through the fence so they couldn't peck at him. I tried everything, giving him hiding place in the coop, but nothing worked, so I removed him from the coop and put him back in the other one by himself. After that, I determined that his vision wasn't the greatest either. When he'd peck at something, he missed a lot.
My 2nd integration, I blocked off an area and made an opening that just the babies could fit through. Again, I put them in at 14 weeks and at night. (after seeing each other for 7 weeks) Everything went really smoothly. They didn't even really use the hiding spot much, unless my RIR came into the coop, she's not very nice to the "new kids". The 2nd day there was a tiny bit of chasing, but nothing compared to the first time. They are now 19 weeks old and they will all lay down together, but the new ones are still kind of a mini flock within the flock. (they cruise around together) There's the occasional squabble (usually over scratch) but everything really went peaceful.