Hey there !! I live in NE OH, so Yes, I cover my boat with a custom cover that came with it. I bring my O'Day 23 home each winter, for backyard storage, so the mast has to come down. The cover goes over the deck only. One trick I learned, from a magazine article, was to buy a bag of Contractor Garbage Bags (the ones that come in a roll). I stretch the entire bag out over the mast, then open them out (width wise) and duct tape them down around my mast and halyards, and then open two out completely and cover my roller furling unit and the top of the mast also. Hope this helps you, or others, but Yes, if you're in MI, Oh Ya, I'd be covering the boat if possible. And make sure you put mosture absorbers in the interior, or you will have mildew in the spring. The interiors will develope their own atmosphere, with the temp.s rising & falling in the fall, winter, and spring. And finally ........ my previous boat was a Catalina 25 and I covered it also. I went to the local Tractor Supply and bought a 20' X 30' silver / black plastic tarp (used to cover hay bails). I also used 1" plastic pipe and bent them over the mast, and tucked them under the safety lines (and tied them down) ....... they worked as supports for the tarp. It was a real project each fall but it worked for 13 yrs. that I had the boat ! Oh Ya, and big heavy rubber bungie cords, down around and under the boat kept it tight with the weight of the snow. OK, enough from me !! Again, I hope this all helps !!!
Bob Burns = Rascal