Aerodynamic bike helmet!

Step 15 Cover the entire plug with a layer of epoxy.

I recommend use of an epoxy with a 90-110 minute working time so that you can relax and put the pieces on carefully. I used West Systems 105 epoxy resin and West Systems 206 curing agent. This has the specified work time and cures overnight. Spreading a thin layer of epoxy over the mold helps saturate the cloth you are about to put on with epoxy (which is your goal).