An alternative idea: Instead of a shelter I bought a full boat cover from Empire Covers last year. An email from them yesterday is touting their sale which has a week to go. I called their Customer Service to figure out the right size; they asked for maximum dimensions for length, width and height at the tallest point (my radar). As a result the cover they sent is generous (actually designed for another, larger boat, I think). It is, I think, their next-to-top quality version, and if I recall it was in the neighborhood of $300. I still needed to rig a support so it doesn't sag in the cockpit area. The cover is a giant step up from the tarps I'd been using. So far it is holding up to snow and rain just fine.