I'm about 80% finished building a coop (link below) for my 7 barred rock pullets that are approximately 3 weeks old. The coop is located on our land that is wide open, so I want to build them a run that is large enough for them to protect them from predators. I was planning on doing a 12' x 24' run that is about 4' high, but I'm not sure that's the right approach. Is this too big for what they need? I want to let them out of the run whenever possible, but they will probably be in the run most of the time since we have dogs running all over the place as well as hawks. What are some suggestions for an appropriately sized run for my chicks?