http://www.lns.cornell.edu/~adf4/cloud.html" [Broken] Has anyone tried this? It looks really cool, and I am thinking about giving it a shot, but I'd like to know how easy it is to get it working, or if there are any other things I should know. One thing I am concerned about is the directions say to use a "metal sheet" but doesn't specify what kind of metal. I don't know if it would make a difference, but I am curious, and I would really like to try this out. Thanks for the help!