I just wanted to share the technique that I used to make my own Foster's Beer Can pot. I was hoping just to score the periphery until a nice circle popped out (as with the pepsi can stove), but 20 minutes of scoring with a utility knife didn't do the trick. These were the steps I used:
Step #1: Scored the inside lip using a utility knife. 10 or so passes would probably do the trick.
Step #2: Drilled 5 1/8# holes in a circle around the top.
Step #3: Took apart the top using needlenose pliers. If you did a decent job of scoring, a fairly neat circle will result.
Step #4: Filed the hole smooth using a metal file.
This process isn't anything special. In fact it's pretty much the same technique Scott Henderson uses to make his Pepsi can stove. Thanks for the inspiration to shave some more ounces for very little money. The beer wasn't bad either. ;-)