The side door is a brilliant idea! It makes sense. I had 45 or so in my last hatch and they swarmed me when I'd clean the brooder, but I spent a LOT of time with them. Now, out in their big coop, I come in from the side and they try to hop out the door or into the front of my shirt! They were 4...
They have a good amount of room. They love to cuddle up-if I just put a hand or foot in the brooder they will swarm over and lay on it! I made the mistake of having them out on the carpet and they all tried to fit in my lap:)