I have a friend who makes "hawk bunkers" for her birds that don't have much cover. . She makes them out of old Christmas trees, or shrubs, or straw bales, or what ever natural material she can find, and they actually work well and are fine as far as cosmetics.. They also have long grass for the birds to hide in. Use your imagination! Maybe try hardware cloth for covering the top of the run, as it is light, but stronger than chicken wire. You can also make "hawk mobiles" using old cd's or dvd's and glittery ribbon, or anything that flashes and spins, like wind spinners, are excellent hawk repellers. You can even buy glittery stuff designed to repel hawks, but just as easy to make your own. You don't need to use many, just strategically place them near whatever your birds use for cover. But if you can't cover the top, you might as well free range, because not only can hawks fly in, but raccoons or other predators can crawl over the top, and some chickens can fly out of the run, too. . AND make sure you protect the bottom too, from predators digging underneath. Hardware cloth is useful for that. Attach it to the run fencing, so that it acts as a "skirt"...or bury it in the ground around the run.