I've had success on gnarly old bumper stickers AND frame stickers with a combo of careful application of the hair dryer heat finished off with Goo Gone if necessary. I have the water-based version, and with a little patience it's been awesome.
Sit bones = ~135 mm, saddles that work ~ 155cm/6.1 in wide
2003 da Vinci (custom road/all-rounder)/Terry Butterfly Ti
1994 Gary Fisher Nirvana (vintage MTB/commuter)/Terry Butterfly Chromoly
1991 Terry Symmetry (NOS frame/fork, project in progress)
1973 Raleigh Super Course (project in progress)