I went zinc. I've read the pro's and con's of aluminum, magnesium, and zinc, and for the money, lifespan, and availability, zinc was a good choice. I travel to Fla, and next year will probably permanently relocate the boat there. Did you get you AC issue fixed? I replaced my salon AC with a self contained Marinaire. I cracked the nylon hose barb from the drain pan and had some leakage and wetness in the area you describe. After barb replaced, no issues with wetness... until yesterday, and thankfully was onboard to see it. Because the drain is mid pan, and the AC is at a small angle, some water always remains in the pan. Yesterday, a very courteous boater decided to gift us his wake going to the fuel dock. I had the bottom of the AC cabinet lined with papertowls to detect any leakage from my barb repair last week... they had been dry, but the boat got rocked enough to slosh water out of the AC pan.. It quickly kly dried up, but a potential source for your water.