Not to put a damper on this informative thread; I'm grateful for the info, but I'm still finding it depends on the postal worker. This week, I shipped chips in saf-t-mailers (in business envelopes) at three different postal stations. The first two went off without a hitch (and at the first one, I even shipped a standard jetpack - though it was white, not manila - and only paid .74¢ to do so). All those packages have been received without a problem. Yesterday, I sent one to the third station, and got a worker who refused to ship it as a large envelope. It cost more than a dollar over what it should've cost. Still, the cardboard method (either a humongous roll like that or the saf-t-mailers) seems to be the cheapest way to go, if you can get the post office to do the right thing.