Update. High SWR! The roof rack rails are metal, and I assumed they were directly attached / bolted to the metal roof, but they are not. The front and rear of the rails are connected to non-metallic base plates concealed by plastic covers, therefore the antenna mount is not grounded. Reinstalled the Stryker Mag Base Antenna and life is good!In the process of installing / attaching NMO Antenna Mount to luggage rack rail on driver's side.