Curious how your new flock is doing and if you've had more predator scare? In my 22 years with chickens I've only had one owl attack years back until now! Mink! We saw it, small, dark brown, bouncy gait, fast. Absolutely THE WORST. Like you've said, very fast, very determined and very hard to keep out unless you have the right gauge hardware cloth, secured, everywhere. The one I've been dealing with plowed right through the cheap,thin hardware cloth that they make pre-fabs coops out of. I had one of those screens over a window and it made a hole in one corner. That is all it takes to get in the coop or run, it was the size of a fifty-cent piece. I'm re-enforcing my chain link run with hardware cloth now and no more free-ranging until this thing is gone or trapped (so far no interested in the chicken livers or sardines in the trap.)