I have a run that is 4'x7' and 4' high attached to a raised coop that is 3x4x3, not including the nest box. So far I have two brown leghorns that are about 10 weeks or so and I'm wondering if I should stop there or try to introduce one or two new birds before the two I have get bigger. I'm considering adding two 5 week old Barred Rocks. The plan is to build a chicken tractor and let them all out to forage daily if I can manage it. I live in the city, but near the river so hawks are common in my neighborhood --having them out of the coop unsupervised is not an option. I'm a newbie to keeping chickens, so any advice y'all might have is certainly appreciated!