I always lash my pole to the roof rack using the old classic boy scout lashing technique. I use a smaller cord ( 550 ish size). Clove hitch on the rack bar, under and over the rack and pole until you're ready to frap around between the rack and the pole, then end with another clove hitch. I've used this same technique to make improvised 2x4 boat racks on the factory racks of cars, too. Then I secure it with the tail ends of the webbing straps for the boat for extra measure. Then I hold onto the previously mentioned pole with my left hand through the open window while I drive for just a little more security (That's not true, but I do find that I reach up and try to move it for the first few miles of the trip to make sure it's not going to turn into a javelin on a hard braking). I've had one of my WW kayaks pass me on the highway once so I like to have some backup and overdo anything I put on the roof rack.