We presently have about 30 hens in a coop that could hold almost 100 with a large run with 2”x4” wire fence 6’0” high which is surrounded by woods on a hill. I have 50 chicks mostly Marans and Whitings which are now 3 weeks old brooding with heating pads in a fenced off area in the coop. At 5 weeks I was thinking of opening a small hole in their brooding area to let them start mixing with the hens. I’m wondering in general how old do the chicks need to be before they won’t be able to fit through the 2”x4” fence? Free ranging isn’t an option because of neighboring dogs and predators.