I successfully mated a CornishX with a turken rooster. the offspring are awesome. I have one naked neck and one full feathered. They are big chickens, though not as big as momma, they are about the size of a buff orpington. They are two of my premier layers, neither has gone broody on me yet though they will be only a year old in june.
When i bought the birds i did not know they were meat birds, because they are called something totally different here in Puerto Rico. Anyway I went and got attached to it and didn't have the stones to kill it when I found out it was a cornish x.
I raised it with my layers, so it had stiff competition for food and didn't get too fat too soon, but ultimately she developed some breathing issues and died.
I'll never raise a cornish x in that manner again. But i've paired her daughters with a buff orp roo. cant wait to see what these chicks will be like.