I am thinking of building a new cage, with no coro, just cubes. It will be a 2x5 with 2 L-shaped upper levels. I am not sure where too find coro, and the cubes are already a little pricey, so can i go without it? I use fleece, but I will make one level a kitchen, so maybe i will use coro there? The two upper levels will be connected by a bridge and the other part is a bedroom where I will use fleece. Could I use a mat under the main bottom 2x5? And then a shower curtain?