Saw an article on using PVC or cpvc pipe bent into arches using stanchions to slide ends over. Creates a quonset hut over boat when covered with plastic tarp. The stuff is cheap, easy to work with, and leaves room to move about the deck. As I have a trailer-sailer I'll probably go to ground level with it. Never liked the shrink rap idea from the standpoint of trapping moisture underneath where in direct contact with hull/deck and clouding paint. I know from car covers that if in direct contact with paint they must be of breathable material-no plastic tarps just laid over the top. I'll dig up the article and post tomorrow.
Can't emphasize enough the damage done by freezing water. Older boats all have some spider cracks, and capillary action will actually draw the water into the crack. No problem until the water freezes. The previous road example illustrates problem perfectly.
If you lay your mast across the coachroof for storage, 2x4s with a hinge between the ends will lay across the mast and prevent your tarp from sagging in those areas, such as the cockpit, and prevent the snow/water buildup in the sags.
For tarps; look around for a discount tool outlet-full of cheap tools. They all seem to specialize in gloves and tarps-cheap. You can get any color you want as long as it's either dark green or royal blue.