Hi. I'd like to upgrade the 2 girls into a larger cage. If I can figure out a tray for it, I'd like to use an animal playpen I already have. 44/44, not sure how many sq ft that is, but it's one large square. 24 high, even though they don't climb or need all that height. Top to keep out the cat! Half by one wire spaces. Any ideas for a tray for this thing/ I think it's a good size, but if you could tell me sq ft and also what you think for a tray/ The manufacturer doesn't offer a tray for this size. Thanks.