The dang hawk came back again this morning! It swooped down and hit the fence. Didn't get any chickens this time. I even waited till later than usual to let them out. And within 5 minutes that sucker was here.
It seems to me that if a red tail hawk can't see your fence, then it also can't see the nylon monofilament fishing line strung over your run. In the real world a garland of garlic repels hawk, at least as long as no hawk has yet tried to breach the garlic barrier.
The second time when it hit the fence. It hit part of the fence that was positioned odd. And from where it was coming from looked like an opening. It's hard to explain. I hung netting over the entire enclosure. Hung CDs. And put foil tape cut in strips all over the netting so it can see it and maybe scare it. It came back the 3rd day and just watched for a bit. Haven't seen it since. Knock on wood.