We tie down on the front bike rack mount with hooks and straps. Front of kayaks are also strapped/cinched down on front goalpost. Rear of the kayaks are also strapped down to front bar on roof rack. When traveling just with the kayaks ( after dropping the rig) we use the both bars on the roof rack. We also have a Curt brand skid plate that goes into the bike rack spot for when the bike rack isn’t on. This keeps the front hitch from catching the ground in uneven spots.
The front receiver hitch is also by Curt and I believe the only one made for the GMC lines. If this picture doesn’t help let me know .