Welcome Scott, I've never heard of anybody storing their M17 that way. It would certainly be much easier to cover the boat with the mast down. Lowering and then raising the mast again in the spring for launching would be less work than attempting to cover her with the mast standing, in my opinion. With the mast down and a tarp draped over it you have a nice "tent" that will hold it's shape all winter allowing rain and snow to slide off with large openings on the ends to allow air to circulate. I would also have some concern about the amount of ice that might form, although it would probably never be enough to cause any danger except for the possibility of large chunks falling on occasion. If others in your area commonly store their boats with the mast up I would check to see how they solve any difficulties that might arise. Good luck to you and welcome to the list. Mark Dvorscak M17 #400 GRACE