We have a nhr very aggresive toward other chickens. Also the thing wouldn't let anyone come or go from the house had to pen him up he was attacking neighbors dogs. Also I have a bantam flock I carry red pyle,& old english. Both seem to do well down to the twenties. I haven't had any deaths from...
For an elevated coop you should have a wire bottom cage. If you want to keep the ground under it clean you should have a steel catch basin built in just below the wire. I have a photo of one example on my profile.