I know you said you were looking for fiberglass, but I'm gonna give you the 24HCF treatment and suggest something else.
Check out a commercial ARE shell with windoors. The prices are similar and they are more secure, hold up better, make easier access to the bed and retain better resale value.
The last fiberglass one I bought like you are describing was $2,700 in 2017.
I bought this ARE for $2,250. Might be something to at least check into. I hate fiberglass shells after using these fwiw.