Chas,
My dealer recommended I don't cut my blanket down and let it hang over on the ends and sides (not as much). It does keep the cover much dryer, not totally dry, but moisture builds up on the blanket so I still have water everywhere when I take the cover off to use it. Have not seen or heard of a way to solve that problem yet, but we'll be wathing for a reply here from the experienced folks. I am sure someone has a solution.
Chaz