Tips on removing signs from glass- Heavy-Duty double-sided tape?

[decalman]

I would first loosen up the glue, with a heat gun, or hair dryer. Then maybe spray some reflective vinyl off in there ( it is odorless and yet powerful )
I don't know what to do next, because I'd have to be there to access, but I know if i was there, I'd have my razor blade on a pole with me.

I'm always removing vinyl.