We free range our cornish x with great success. We find the freedom rangers to be mostly hype and they do not grow much faster than say a barred rock cockerel, white rocks, or even a new hampshire red. The cornish x can be good free rangers if given a chance. We let our 50 or so cornish go where they please and they would venture a good distance away from their shelter and eat plenty of grass, bugs and any of the other goodies you would expect. They also will take about a week or so longer to grow out due to all the extra exercise they are getting. We don't have any problems with flip, though we did have one unexplained death at about the 1 1/2 week point in our last batch. We find the free range cornish to be a bit better in flavor as well as texture. Happy chickens=tasty chickens. So I'm just saying maybe don't count out those cornish x yet. Any other chicken is going to take almost 4 to 6 months before they are ready for processing and at that point we find them a bit tough. Good flavor for soup but hard to chew coming off the bbq. Either way you go good luck.
Chris