I would really like to know what they use for those all season parks that they have set up. It is some kind of special Astroturf. But What you should really do is make your drop in like a roller system. Go to the link and check it out. It is the same type of thing they use at a warehouse for their packaging line.
http://freeskier.com/freeskier/news.php?action=load_story&news_id=1102