Ah... ok. Yes, I would think the 5 mil would be too spongy. The 2 mil is really perfect. The one drawback is that the material, especially at only 2 mil, is a little fragile. You could tear it with your hands if you wanted. But if you mounted it to something, it should be fine. I like being able to roll it up and go though. I've really been enjoying this thing. I guess if it tears, that's another 89 cents down the drain lol