What a great thread! I don't know if there is a lot of experience on here with this, most folks build a solid coop that is good enough for winter. I myself have a lot of OPEN coops, no walls or few walls.. and so was going to build "Perch Boxes" I was calling them, but I like your "huddle box" name too! Conceptually, a box surrounding their roost so that they may stay warmer in the winter when sleeping, and for me to avoid as much frostbite as is possible. I haven't figured it out yet, with few walls I have little to attach anything to, but am trying to figure it out. I was even thinking a nice large cardboard box would work as well, centered on the perch with an entry hole along the perch. You clearly have room to just throw up some plastic or even paneling/plywood to enclose your area for them. Nice coop by the way! I hope to see more responses along these lines. I actually think for my roosters, I might give them a nest box of sorts... they won't perch, but they will stay warm in a bed of hay. I use plastic storage totes for nest boxes, I suspect they will work well for a rooster bed too.