My cornish x's are still growing but I ordered from Meyer hatchery here in Ohio. It's not very far from me and they seem to have very nice chicks in all breeds.
I've had several of them hit 7+ pounds in 8 weeks in Fall batches, but never in Spring/Summer batches. They seem to eat a lot more when the weather is cooler. Makes sense, I tend to eat less when it's hot.
I got my birds from Quality Supply. not sure where they getthem from. Help a friend butcher on Sat. his birds were 5.5 lb average. w on bird at 7.25 lb. it looked like a small turkey.