I would not worry about a little dimpling, it won't hurt anything. Sounds like you need to have better support for the work piece. What size did you make the Smart Table top? Did you have the Smart Table arms extended? With a 2'x4' top and the arms extended there is only about 1' of material extending past each end, the 8' work piece should be supported enough to prevent bowing when you have the saw at the end of the rail. What kind of material were you cutting?