Check this out...havent used it at the lake yet, but should work great (knock on wood). My shredstixx elevation doesnt fit in my racks, and I didnt want to spend another 300/400 bones on an endless wave rack.
These are meant to be used on the roof of you car, strap them through the windows basically. Instead I strapped them to the cross members of the tower, board clears where the rope attaches by about 1.5" and I doubt it could hit even if you wanted it too.
Here are some pictures