Oh my, your problem brings back memories... I do not have good news - it was awful getting that stuff off mine after around 6 years. I made scrapers from plexiglas, and used a heat gun. There were many, many hours involved. The plexi scrapers worked reasonably well, but they were fairly narrow IIRC. Too wide and one can't get the pressure needed. I tried various solvents, but since mine is painted under the tape, I didn't want to get too aggressive.
For those not following why this is a problem - the polymer crazes and cannot be pulled off. Small shards come off instead.
Patience....