A quick post to the Model Car List (https://groups.yahoo.com/group/ModelCarList) got me a pointer (thanks, guys!) for using older decal sheets that may have become brittle, or newer ones that are thinner than in the good old days: spray the decal sheet with clear (for example Testor's Glosscote), and let dry for a day before cutting and applying. Too late for the first decals on the Speed Build challenge, but it'll come in handy when I do get around to finishing up the build of the Honda Mugen Civic racer.
Ah, the Internet. Source of infinite wisdom.