Get some heavy sewing thread, and slip in in through an unglued area. You use it like a wire saw (albeit, tiny) to work your way through.

Would be good to have three hands to make it work, really needs a good clamping method, that I never really mastered.

I did manage to get a goo ball out of an old Firebird with it, though. I have another idea that I will be trying for some other built ups that surfaced a little while ago.