I tried the Cornish X's twice, both times with six birds. We free-range our flock and leave food down 24/7. We didn't have any problems with the meaties as far as walking, heart attacks, etc. What I noticed is that those six birds stank more than my other three coops put together! I was cleaning their coop daily but it was always nasty, even though the guys were outside free-ranging during the day! Also, I'm too soft to process them myself and the only one I could find in our little town wouldn't pluck them - he skinned them and gave them back to us not well cleaned, charging us half the birds! Out of the 12 chickens, the guy who processed them for us kept six. The six we got back were delicious, except we had no skin, so we were limited on our methods of cooking them. Food cost and processing cost for substandard results made us decide to go back to grocery store chicken, so that experiment didn't work for us. If I ever find someone in Brooksville to process them (or if I ever grow a backbone), I would love to try it again.
BTW, our guy told us the meaties had crops full of grass.