Yep Harpo, i actually have some of those and use them they work good if i could keep the moisture out of the boat.
The problem i have right now is every time it rains the boat gets drenched, when it rains for days i cant dry it out until it stops. At this point i need to keep the water out thats my biggest problem. This cover has always leaked a little but now its really bad, an insect screen would be just as effective as my cover right now.
To give you an idea of how bad it is. About a month ago i forgot to take the plug out, i had about 4 inches of standing water in the floor of the boat after a day of rain. Like i said my cover is useless for rain right now, there are areas that are so bad thru that i can see thru the fabric.
The part that really kills me is i paid good money( somewhere around $450) for this cover when i bought the boat, its never seen snow and only gets used when the boat is in service. Otherwise the boat gets shrinkwrapped and the cover gets folded and put in the house. It has not stood up, my last boat had a much better cover that they GAVE me when i bought it. It was the shipping cover that was made of heavy canvas, it was totally waterproof fit like a glove and worked great. I put a strap kit on it and trailered with it too. The guy who bought my boat still uses it, that cover is 9 years old now. My current cover is 4 years old and its trashed, the leaks are driving me nuts not to mention the seams are all tearing( they are renforced well at all)
Right now the boat is sitting in my sisters garage until we get a decent stretch of weather where its not raining or i get a new cover.