Sounds like a great strategy. I would make the "tunnel" at least 2-3ft wide so birds can get past each other easily and keep 2 more sources of water in the "extra run"I’ve been thinking of a solution to give them more outdoor space. I have a side yard on the same side as the coop which is on my north side and I don’t use for anything. I’m thinking of creating a tube or tunnel to the side yard and then gating it off. This would create an extra “run” that would be pretty predator resistant.