I sometimes think people worry too much. Chickens are very alert when fully grown. I think it is more important to have places readily available for them to hide under if they fill threatened. Now don't get me wrong , if you live in an highly predator environment it may be needed but in my 30+ years of raising chickens. I have only lost a few chicks to predators. I have never lost a fully grown chicken to a predator. My girls are out all day and go into there coop voluntarily each evening. There are plenty of places for them to hide under if they fill threatened . I have hawks and cats and possums roaming around all the time and my girls will let you know when someone odd is around !! So you may want to just add a little cover for them such as a simple pallet stacked on some blocks or anything you can come up to that looks cool. Just sharing some thoughts