@mlowen
It looks like you are using your tunnels to primarily move chickens from one covered area to another. Are all the areas that you let them into completely covered over the top for hawk protection?
The tunnels are to move from one area to another. I have hot pink string up in the yard and behind the coop. I don't know that it really protects from hawks. My hope is that it at least looks weird enough from the sky that it gives them pause. My town's ordinance requires chickens to be behind a fence at all times and I can't afford to fence my whole property--small though it is.