I’ve had various experiences in fences with chickens. Whether or not they get out has a lot to do with motivation. If they really want out they can perform feats of magic. If they don’t want to get out it doesn’t take much to keep them in.
Even if you know all the neighborhood dogs are safe a stray can come by at any time. Chickens are prey animals. When they are not in Fort Knox they are at some risk to digging, walking, climbing, or flying predators. Some people can go years totally free range and not have any predator attacks. Others are wiped out almost immediately. You are dealing with living animals, the chickens and the predators. No one can tell you what will happen, just that something might.
The bigger the run the harder to make it totally predator proof. You can make them pretty predator resistant though. Covering a 2400 square feet run could be challenging, especially if you have to consider snow and ice load.
Chickens like to perch. If the top of your fence looks like a good place to hop up to and view the world, they just might hop up there. Who knows which side they will hop down on? That’s one way chickens often get out of a run.
I’ve seen chickens do some pretty impressive fence climbing. A hen trying to get away from an amorous rooster and trapped against a fence can climb up really well flapping all the way. When my adolescent cockerels get in pecking order/dominance disputes the loser will often go pretty high straight up if it is against a fence and cannot run away. They just might come down on the wrong side. I use 4’ high electric netting and have noticed that when I set it up in a long narrow configuration I have more escapees but with a fairly wide configuration I practically have none. Adolescent cockerels can be a pain though.
One trick I’ve learned to make a fairly tall fence without it costing a fortune is to build the bottom out of 5’ high fencing materials and use some strong posts. Then I attach a second piece of 5’ wire fencing onto that, overlapping the top by about 2’. By attaching that wire at both ends of the 2’ overlap, top and bottom, the wire is stiff enough to stand up and give you a fence 8’ tall. The top is wire too so the chickens don’t see a convenient perch up there. In theory if a raccoon, fox, or bobcat try to climb over that he fence is limber enough to bend back over the animal, making it really hard for them to climb in. Corners and such can be weak points but maybe it helps.
I get really good containment with my 4’ high electric netting. I know my full sized chickens can easily fly over that if they so desire but they hardly ever do, just when something strongly motivates them. I don’t clip wings either.
I have no idea what will actually work in your situation. I wish you luck figuring it out.
