times in Mexico. As Gene suggests the issue is always venting. Moving air around is your defense against mildew and the various molds that will attack. I had a full boat cover for Brendon when I first bought her. I installed it thinking it would keep the boat cleaner and cooler while I was living aboard. Wrong on both counts. It dramatically drove the temperature up and trapped the dust. I ended up cutting the lower half off so it would cover only to the lifelines. Then I realized that it was such a PITA to install and remove I never took the boat out. I had limited storage at the time so I pitched the thing. Later, when I went down to Mexico I ended up making another complete sun cover. Again, just down to the lifelines but with a small 8 inch flap hanging down just below the lifelines. So I guess my position on it is to let your friends remove the cover. Have someone open the boat and air her out ever couple of weeks and keep a fan or two going. I left Brendon in Mazatlan for a couple of months in the summer and had a professional boat sitter checking on her. Two days after I left the air conditioner picked up some debris in the intake and packed it up. The boat sitter put a couple of small AC operated fans inside to move the air. When I got back she was fine but the fellow in the next slip just left his closed up and no sitter. When he returned he spent two days cleaning mold up. He was not a happy camper.