I have black fiberglass on my 2 forms.
I used a spray on adhesive 3M "High Strenth 90" to glue the glass to my wood forms, it says it's heat resistant on the label..
Big Jim, I wonder if 3M 5200 marine sealant would hold up to the heat? I have used it to "glue" aluminum to fiberglass boats..the 3M 90 may work too..