Re: snap stains
It also could be the snap areas are the low point on the cover and that is the path the water takes,it runs down the sides of the fiberglass.
If its kind of a black looking stain its from the dirt that gets on the cover and chemicals from the rain water itself.
Common problem here in the Southeast US. My fiberglass sided. RV and the boat gets these stains.
Walmart sells some decent spray on stain remover in the RV supply section that is safe for fiberglass.
I spray that on,wait a few seconds and wash it down with good car wash soap.
It stays clean for a couple months then do it again.
