They'll be good for small fryers at that age. The meat chickens that you can buy can be processed at 8 weeks, but the "normal" chickens aren't big enough at that age. You'll probably only get 1/2 the meat from the chickens you're talking about at 4 months of age as you would on the meat chickens at 8 weeks, but since you're hatching them anyways you may as well use them! You may have to slow cook the ones that are 4 months old as they start to get a little tough at that age. As long as you know not to expect chickens w/ a lot of breast meat like you see at the store then it should be a pleasant experience.
