Rubber foam mats

[wallawu]

If you're willing to get out there and clean it daily I guess you wouldn't need pine shavings. The added cost for me makes up for the convenience of being a lot less work, but one bag lasts me over a month usually because they're only in there at night with no food or water. I'd just worry about your seams as someone else pointed out. I guess you could seal those up, but that sounds like a lot of work, too. Keep us updated on those things. They may be a good alternative to some other methods on here.