I went to a class on sunbrella and they talked of a person who complained of mildew on the sail. They said no matter how many times they water proofed the sail cover the sail still mildewed. We were told the cause was the water proofed sail cover. That the sunbrella used for that is to keep the UV off the sail and that water proofing it only kept the moisture in causing the sail to stay wet. Just passing this along for info. I had no idea how many types and grades sunbrella made. An incredible array of uses
That derelict boat was another dream for somebody else, don't let it be your nightmare and a waste of your life.