Carburator cleaner in the spray can will get just about anything off.
It seems that damage could occur however, it evaporates so fast that I
find that as of yet, (knock on fiberglass) I have found it to be
effective and without damage. Try a hidden spot first and try at your
own risk as this is not the normal use for this product. I used it to
get some cloth gap tape off that was firmly attached.