it increases the distance between the tunnel and the skid, so i guess you would say it does both.
to make your own, you just need to build a bracket that you can bolt through the existing tunnel bracket and hang down the desired amount with a hole in it sized correctly for the bolt that held the rear part of the skid into the stock bracket. i always used aluminum plate and dropped down about 2 -2 1/2". sometimes the other mount points would need to be let out a bit as well.