Wow been ther done that. Your temp's wont be incredible. You will probably nitice a 1c drop or so. Here are some pics for you to give you some ideas:
http://community.webshots.com/album/30591091AJTJcfZzkJ
I also caame up with a second version that was bigger with a bigger silver pice in it that did much better but I don't have pics of it. I'll try to post them in a few days.
Don't pay any attention to the temps listed there the system was not set up correctly.