I'm glad that has been effective for you and your flock. Our flock has a ton of places to hide, including numerous shrubbery, secondary growth trees, and old growth trees. We have a garden and landscaping designed with them in mind. That did not deter a red-tailed from killing my hen this winter in a narrow span a few feet wide between mature trees and a garden (along the giant sunflowers), nor did it help my hen who was under a canopy evade a falcon the year before. The hawks I've scared off this last week were all in the branches of a giant fir tree. The rooster had all the ladies bunched up under a branch and was yelling out the alarm, thankfully. For sure, plenty of cover is key, but even so, when you live in a raptor migration area like we do, the pressure can get pretty serious. Falcons particularly are built for getting prey in forests. I've thought about adding guinea fowl to the farm. We are too close to neighbors for peafowl..
I think the fact we've cut down all the old tall trees all around with the neighbors has added to the safety of our flock - no place for critters to hide and pounce. I hope your Guinea Fowl idea works for you. I always feel so bad for chickens getting caught by those nasty aerials! Our neighborhood Crows in big flocks are excellent chasers of the lone hawks that come around!