It isn't necessarily a bad thing, as long as it doesn't freeze in there. I don't think you can really expect to keep it out. The stainless stock and the fiberglass shell have wildly different thermal expansions, so opening up a crack in that area is a given. The key if you spend your winter out of the water is to let the water out of the rudder. I've drilled a few drain holes in the bottom of mine, which seems to have solved the 'puffy rudder' problem that I had years ago.