Dice - Copper vs Aluminum

Hey guys, conroe is around the corner so I'm going to build my DICE container so I can be ready (and perhaps due some D805 tests too). Anyway, I have all the tools that are necessary and read all the articles that google had on DICE container making. One topic I didn't see covered and have a question about is material. I understand Copper is a better heat transfer metal than aluminum but what would be the actual difference? The cost of metals for a copper piece seem to be about twice more than aluminum. So is it worth the cost to go copper or just stick with aluminum. Thanks.

p.s. Any online places to get copper piping? I saw onlinemetals but they dont seem to have copper pipe over 2" OD. Thanks.

Aluminum (for some reason I have not seen explained in much scientific detail) REALLY sucks as a conductive material at temperatures below 0C. It's not as efficient at conducting as copper at any temperature, and a few people who have done side-by-side comparisons between the two materials when it comes to DICE containers the Aluminum containers had temperatures that were 20C higher.

For copper http://www.mcmaster.com is a much more comprehensive source. Copper pipe is (no big suprise) expensive. You may want to call a plumbing supply store, or even a plumber, and see if they have any 2" copper pipe scraps.