I had looked into those, but I needed longer ones. I have seen other people using rubber exercise mats- the ones that lock together. They should be safe as long as the rabbit can't chew the edges. You might want to cover the edges with something so they can't eat them while they are out playing.
I know this is raising a very old question and that's bad net ettiquette but I also am considering this route. A rubber cow mat only costs 40 bucks (weighs a lot though) and involves no minor construction setting up. Would vulcanized rubber be safe around a rabbit though?
Wow, the stall mats I'm thinking of weigh 100lbs each. We used them in the livestock stalls when my daughter was in FFA. It would be a major deal if you needed to move them to wash them. They can still be chewed on by a determined rabbit. We had the small interlocking rubber mats in our French Lop's cage. He never bothered it while in my daughter's apt, but tore it up when she kept him at our house over the summer.
Yeah the one I got weighs that's much. I like it, its sturdy and Conan rarerly chews on it. I would almost feel I made an excellent choice except for the fact that often smushes his cecals which get in the grooves. Those are hard to clean!