it has been my experience that if it's too tough to get off the plate, it hasn't cooled long enough.
sometimes i leave my stuff over night and when i come back in the morning, just touching them will break them loose from the glass.
that is also using hairspray on straight glass. i think once that stuff dries and the plastic cools it lends it's self for easier removal.
with tape or other materials, the print may be "gripping" to much.
on straight glass, there isn't much to grip too.