Hey Steve, the more I think about it, if I had to store any of my boats outside, I would build a proper box for it. When you consider that your Caribou is worth at least 3 grand, a relatively small investment in some 2X4s and some plywood and paint would be well worth it. I would cut some vent holes and cover them with tight screening. I would make the top removeable in two, or three sections. Put some nice soft foam rubber on the bottom and you're in business.
If there are any freight hauling businesses around you, you might be able to pick up a shipping crate that could be modified for little, or nothing.