I know ethanol and fiberglass don’t mix. It cost my brother 18 grand to replace his 3 factory installed fiberglass tanks in his 36 yellowfin. The previous owner put ethanol in them n the racors were filling up with fiberglass strands. Nothing I own has ever had ethanol gas except for my truck. The tanks that I have repaired were done well enough with the marine Tex (actually pc-11) compound so that no gas will ever reach the fiberglass. I have even fiberglassed brand new tanks so the corrosion can’t even start.