I know this is a very late reply but I thought I'd give my $.10
The best way to remove jeep pinstriping is to use a plastic chisel and a hair dryer. I actually used part of a plastic lightswitch cover that I sharpened a bit with a file. Works great just be patient. Also, if you have a fibreglass hatch, the heat isn't conducted under the stripes so they're more stubborn.
Do NOT use a medal chisel or anything abrasive!
Soaking it in WD40 is another alternative.