Use some laminating epoxy (FG is optional for 4â€ Diameter kits), and some Mylar. Smooth the epoxy under the Mylar to wipe out any air pockets. Donâ€™t stress the excess epoxy drooling over your fins. Once everything is dry, use 80-100 grit sandpaper on a palm sander (heck, even a hand sander) to sand this all away. Make sure to wear a mask, glasses, gloves, and a long sleeve shirt as the dust gets everywhere. Have the shop vacuum close by!