I thought I'd share my idea of baby-proofing the C&C cage here. I know most people use cardboard, but for me and my living room that just looks too nasty.
I bought a large roll (36x60 inches) foamsheet from Michaels (a craft store) and cut it into 10 inch high strips. I stuck the strips between the coroplast and the grids, holding them in place at the top with binder clips.
I think the regular price for the roll is $7, I happened to get it on sale for $5. The cool thing is that when I'm done with it I can either roll it up and save it for next time or use it for other crafts.
Here's a pre-binder clip pic:
