Re: problems with your cover
my cover is lame. It's a generic blue one with 4 black nylon straps that are sewn over the top. Then they have buckles that connect to straps that go under the boat. The edge has elasti-cord sewn into it. The problem is that the buckles aren't right at the edge of the top, they're about 6 or 8" up. That means even when the straps are tight, it is only the elasti-cord keeping the seal around the boat.
Even though it was supposed to fit the beam of my 16' boat, it seems a bit undersized. To keep the edge of the cover from sliding up, I have sewn some (about 10?) 1" nylon loops with plastic D rings around the edge. That way, in addition to the nylon straps, I use a cord/rope either under the boat, or to the trailer to keep the edge down. It makes it a much more more snug fit and water sheds better.
I also use wood batons to elevate the cover a bit, but I need to add one more in the front area because water can still pool there (no windshield on my boat).
I still intend to build a sort of ridge pole and use a big blue tarp over the whole thing this winter.
All in all, I think I would've been better with more of a "heavy duty" cover... one with an attached motor cover would be nice.