Providing a safe place for chicks to duck into where the big chickens can't follow is only half of what you need to do to make a run safe for the chicks as they're integrating.
I have a complex run with numerous partitions, and early on I could see that there were a lot of places for a chick to get boxed in or cornered or trapped with no possibility of getting back quickly and safely to their safe refuge. So I created "portals" in all of the partitions and anywhere it was possible for a chick to get trapped for that's when injuries and death occur.
I've been using this system of portals for eight years now without any casualties. I have pics of my set-up in and article I wrote on outdoor brooding linked below my post.
From how you describe your run, it may be a long distance for a chick to travel to find its way back into its safe refuge. You may need to re-engineer your run to accommodate safety for chicks. What comes to mind is a parallel channel with openings all along the way or an opening along the bottom a few inches high that chicks can scoot under.
I have a complex run with numerous partitions, and early on I could see that there were a lot of places for a chick to get boxed in or cornered or trapped with no possibility of getting back quickly and safely to their safe refuge. So I created "portals" in all of the partitions and anywhere it was possible for a chick to get trapped for that's when injuries and death occur.
I've been using this system of portals for eight years now without any casualties. I have pics of my set-up in and article I wrote on outdoor brooding linked below my post.
From how you describe your run, it may be a long distance for a chick to travel to find its way back into its safe refuge. You may need to re-engineer your run to accommodate safety for chicks. What comes to mind is a parallel channel with openings all along the way or an opening along the bottom a few inches high that chicks can scoot under.