I just noticed this as I am redoing mine. I'll have to see how that works with 2x6 bunks like I have. FYI back when I worked for the government we had this booth that had a booth with a 40lb sliding window. The bottom track was long since gone and the aluminum was eating right down into the frame. This window got opened and closed about once a minute all day 24/7 . Of course being cheap GSA just wouldn't fix it so I ripped a piece of PVC pipe down the middle and slid it down there. The thought was that when it wore out in a month I would put in the other piece then repeat as needed so nobody had to drag that heavy window over that grating cutting mess of ragged aluminum.
Long story short it lasted 3 or more years until they finally rebuilt the whole booth. Figure that the heavy window slid back and forth a minimum of 300 times a day and it's amazing that it lasted at all but it did. So how much wear do you figure a boat sliding over it occasionally is going to have, none. So now to find a piece of PVC that I can coax into a more or less flat surface and I can get 8 inches of width out of . Then I can screw it from the sides.