In this thread are suggestions to use the aluminum from beverage cans, sanding them on both sides. Sounds good to me. Also copper foil would be great, as has been mentioned here. Perhaps you have seen the recent thread about the guy selling P60 dropins on ebay. He makes some strong claims about the superiority of copper foil and thinks aluminum foil is better by far, than electrically conductive copper tape. My tests were not nearly as clean as his graphs portray. The time that the fully charged battery was off the charger seemed to have more of an effect on my results than type of wrap. The tightness of the fit was of course very critical to performance. The act of screwing the flashlight together after replacing the battery seems to generate heat from friction, as well as the warmth of the hand on the flashlight, all affected the 'ambient' initial temperature of the flashlight. While I plan on getting copper foil without adhesive at some point, aluminum foil, applied smoothly and very tightly, as Vinh recommends, has worked the best for me so far.
