Ok, I can tell you the methods I have seen used first for foam for craving foam, xacto blades and sharpen clay sculpting tools, for replacing foam expanding spray foam or craving a piece of foam of the right density and glueing in. When working vinyl with heat gun making extremely small cuts sealing with vinyl repair tools (liquid, powder vinyl, and irons) . Cuts on vinyl can get out of hand real quick and 50+ year old foam can turn to dust real fast. I recommend practice on a cheaper already damaged piece . Hate to see a nice original piece get ruined. Check online see what others have done for similar projects or aspects of what your trying to do. Also dash direct used to do custom work maybe they still do., either for the black one or your aqua.