Mine is a Gen II, so there may be a few differences, I don't know. Set the system in the truck with the bed rails of the system sitting on the bed rails of the truck, remove the 4 bolts holding the "top" of the system bottom skid, these are on the bottom part of the ladder rack uprights. Adjust so the skid rests on the bottom of the bed and the bed rails touch the trucks bed rails. Drill 4 holes, 2 on each side, through both the system's and the truck's bed rails, and bolt with stainless bolts and lock washers. This holds the skid in with no drilling in to the bottom of the bed, where water and chemicals can eat at your truck.

Most advised that I skip this next step, but A.C. advised I do it, and it stiffens up the system. Re-drill the 4 holes in the uprights that that you removed the bolts from to adjust the height of the bed rails, and re-bolt them. This also helps if you ever remove the skid, it stays adjusted and together. I used nylock nuts and lock-tite red.

Hey Brian, I can take some pictures of my mounted Gen III skid tomorrow and post them up here if that would help.