In the south I think fiberglass insulation will collect more moisture from humidity than the insulation value will warrants. If you are running the AC you will reach the dew point somewhere in the thickness of the insulation. In the summer in New Jersey my parents house at the shore and over dirt, with exposed fiberglass insulation, would be dripping wet during the summer. If you have the pan off I would consider a spray on vapor barrier like undercoating, frame and floor.
WBCCI 12156 AIR 3144 WACHUNG TAC NJ6
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles