I regularly integrate 5-week-olds to my flock of a mature rooster, mature hens, and often juveniles of various ages. I've had a couple of broody hens wean their chicks at 3 weeks of age, leave them totally alone to make their own way with the flock. They did. To me size isn't that critical at all. How much room you have in the coop and run, how you manage that room, and how those areas are connected are of much more importance than size of the chickens.
I have no idea what your coop and run look like, how many other chickens you have, or your flock make-up. My brooder is in the coop so the chicks grow up with the flock. Yours have been in long enough so they should be OK on that aspect. My coop is fairly large with lots of hiding places. Outside when my facilities are crowded I still have over 60 square feet per bird, mostly juveniles growing to butcher age. I have weather that mine can be outside all day every day. In WV you should too. Mine stay outside all day every day except when they are in the nest laying. Mine young ones form a sub-flock. They avoid the older ones as much as they can all day and all night.
I don't know enough about your situation to be able to offer real specific suggestions. In general give them as much room as you can. Improve the quality of that room if it is tight by adding clutter, things they can hide under, behind, or above so they can break the line of sight. Offer feed and water in widely separated places so they can eat and drink in peace. Don't try to force them to be together in tight spaces hoping they will fight it out, it doesn't work that way. Don't expect them to all sleep on the main roosts together, mine don't. I don't care where mine sleep as long as it is not in my nests and is someplace predator-safe. They will work that out later.
Some chasing and pecking isn't a big deal. If they have room they learn to stay away from the older ones. If they don't have enough room to run away and get away, let alone avoid them to start with, it gets dangerous. To me when it has gone too far is if a chicken lays down and tries to protect its head while the other chicken is trying to attack the head. That's generally when chickens get seriously injured or die.
Sometimes this stuff goes so smoothly that you wonder what all the worry was about, even if it is crowded. Each integration is different because each chicken has its own personality. My suggestion is to try it when you can be around to observe and base your actions on what you see. Good luck!
