I looked into raising mine properly. I'm feeding them lower protein grower b/c I didn't want them to grow too fast. They are free ranging along with my layer flock. I have one CornishX pullet who runs as fast as my layers when my roo calls that he's found treats. I still feel AWFUL for them, and won't be buying them again. It looks like they're in pain when they walk, and mine do have to flap while running to keep from tipping over. And it's only May here in the sunny South, and it's so hot and humid, my meaties DO flop down after a few steps during the 2nd half of the day. In the morning, they are up and running with the rest, but all that energy is gone by late afternoon. They pant all afternoon and night long. They cry in the evening when the rest fly up to roost and they have nowhere to go. They climb as far as they can, which is usually about 6 inches off the ground. They still have the instincts of a lithe normal chicken, but they have the body of a hippo and can't do what their brains tell them they should be able to.
btw, I will continue to buy them from my local farmer at the farmer's market, but if I ever do meaties again, I will try a slower growing breed like the FR. I would rather be out more money feeding them or having to buy at the market than to watch them suffer in my yard daily. I feel like i"m giving them a much better life than they would have had in a commercial farm, but I don't want to see it. I actually prefer darker meat anyway, and I think the flavor of layers is superior to CornishX as well. Especially my Delawares. They are delicious! And their breast are twice the length and half as thick as a CornishX, so it probably ends up being the same amount of breast meat. Same for the legs.