I have the same brooder set up but I am using puppy pads rather than shavings. How are you finding that the shavings work out for you? Do they kick it out a lot over the cardboard you have on the walls? Mine kick their sand all over the place and I have cardboard up too, I cant imagine how shavings would be but I'd like to try it.
I like the pine shavings. I keep a broom handy, though, because not only does the Barred Rock and the Australorps kick the pine shavings out, but the feed, too! Not a lot, but enough to make me have to sweep periodically. I really don't mind - in a few months they will be supplying me and some friends with eggs.