I used Tule hullaports (J shaped with straps) on my factory racks and it sucked on freeway, because of the length and weight of both kayaks I think. Not very stable. If hauling just one kayak just put pads on the factory rack and tie it down to the rack. Hauling it with what you're talking about should work much better than the j racks with kayak on their sides. Mine are both 12' and with both of them with the hullaports on the factory racks, comes close in weight to maxxing out the factory rack rating. I just use truck for my kayak hauling nowadays so if anybody is interested in some hullaports then well..........maybe I'd part with them.