Bountyhunter:

I've bought gaffer's tape from this outfit, and it's good stuff IMHO. You can probably find tons it online by looking for Permacel.

http://store.yahoo.com/cinemasupplies/permacel.html

I don't know about LONG-term tests, but I stuck a piece of it on the back of a metal filing cabinet. A month later, I ripped it off. There was no residue or film left on the cabinet, and no degradation of the adhesive. Mind you, this was in a stable, indoor environment.

You can also find gaffer's tape that's specially designed to be used outdoors, and is waterproof.

I got some international orange tape and wrapped four or five feet in a flat pack to replace the silver tape in the ETS kit.

Bear