The windowsill of a stock Mustang curves down, then levels out just behind the A-post. Ours runs level, from the top of the front fender all the way to the C-post. It provides a little more protection for the driver and, we think, looks a lot better on a race car. We filled in the gap on the rear fender with a piece of steel tack welded into place. Chris dad, Eddie, is going to paint the car for us and swears that with a little seam sealer he can make this little piece of patch work look like it just rolled off the assembly line.