The New Hampshires and the White Rangers from Freedom Ranger hatchery are the next meat birds I want to try.
I butchered CX from 5-9 weeks, and that last week or so were tough - had 2 heart attack losses around 8 weeks. I had one 9 wk old CX fall over on her back while trying to drink from the nipple waterer, and couldn't get up (I flipped her back over so she survived). Definitely wouldn't do more than 9 wks, and prefer to process at 8 weeks if I could.
Based on reviews, the Ginger Broilers were supposed to be pretty docile yet still active, a slower growing broiler. More active than CX, yes, but docile? Not so far. We'll see how they do once they make it outside.