Nick
I used a 10mmx1mm black foam neoprene tape.
Just as a precaution I would check the compatibility of the paint with the type of window plastic material. Some have a reaction to some paints that is like a surface stress cracking that can go deeper near edges. I had this problem with side windows that had been supplied by GTD when they were still in business, the type of solvent in the paint may be the cause
Steve