The only thing to watch on the wally world covers is the straps on the cover rot pretty quick, at least on mine they did and it was less than 6 months old when they went bad.
Dropshot, The owner of my Javelin had one of those heavy blue covers custom made. They range from $200.00 to $700.00+. They are trailerable water proof and duriable. The one on my boat has lasted for years and still looks new. Granted that in the past 5 or 6 years the cover has only been on about 1 or 2 days. but, it is really holdng up nicely in the Rubbermaid tote its in emoCool