Daryl: Thanks for posting. It's nice to know that if I was away from home, I could make waterproof maps in a hotel room after a trip to any grocery store. Usually, my time is worth more than that, since I keep "Rite in the Rain" paper around and it is somewhat light (6.4 grams / 8.5"x11" sheet) and cheap ($0.15/sheet when bought in 200 packs). But in a pinch, or for 2 or 3 copies, that's a nice trick.
Now to REALLY save weight and multi-task your gear, use that technique to get get ink onto 8.5"x11" sheets of plastic, but then bond them onto your trash-compactor liner bag so you have a multipurpose pack-liner, map, emergency poncho, lower-leg bivy sack, funky rain hat, and trash bag.
Bonding them together onto a larger sheet also solves the edge-of-the-map problem*.
Seems there should be a tradition of handing off northern maps to southbounders and vis-a-versus on the AT. But I'd assume many more people go north to optimize the seasons as all through hikers on the PCT have to do.
*You know that Greenwich England is located where it is in order to maximize map sales? Because 0 longitude is there, all moderately interesting places all on the edges of two maps and the really cool places are at the corners of four maps.**
** You know that the above is a joke and Greenwich is at 0 because the English solved the Longitude Problem first? My father read "20,000 Leagues Under the Sea" in the original as a boy and tried to track the progress of the Nautilus. Which at times seemingly went under land. Because the French, being French, thought Paris was the Prime Meridan.