I put this in another forum.... hope it helps.
Walt wrote:
I've got one on mine. Cost about $900. Go to
http://www.fourwinns.com/gear/canvas . I can get you a part number from mine to reference if you like. It just survived two ice storms and the first 2 inches of snow and I've only had the boat one month! Sad to say my boat has seen more snow than water!

Underneath the cover you see are my snap-on covers, with the standard posts, etc. The "top" cover has vents on the side which allow air to circulate. I've done this for years on my previous boat without the ill effects of mold and mildew. I do trailer uncovered to ventilate. My old boat had a faint smell of gas when I'd overfill, then cover it. This one also has holes for the pop-up cleats. You say you want to cover it moored.... this would be a viable option.
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Walt B
"Debt-Charged"Black '07 H210SS6.2L Bravo One turning a 21P HIFive
Wakeboard Tower with Perfect Pass Stargazer version
Missouri River; Kansas City, Mo.