Still not much progress on the spare rooster cage... That is, I whipped up a decent cage in about an hour using the compost panels (sets of 4 mesh squares), but haven't been able to join the play mats in such as way as to make them sufficiently sound-retardant. Individually they're not big enough to cover a full side, so there would be lots of joins where sound can escape.
At the moment I only have the two mature cockerels and both are sleeping in the night-shed, so it's all fine. The night shed already has insulation (see my earlier post).
What I'm trying to do is find a way to keep spare roosters, as choosing which rooster to keep before the crowing ramps up isn't the best way to retain good breeders. Sometimes these birds end up having a temperament or health problem that wasn't obvious at the time of selection, when they were very young. Or sometimes they might not prove to have the characteristics I want. At 16 weeks it's a bit of a guessing game.
I'll keep searching for a way to make the cage-cover, and let you know if it works. If it does, it might be a cheaper way to keep roosters quiet than building a purpose-built shed, and it would always be flexible and easy to store (just undo the c-clips and flatten the cage).