Assuming you have the factory rack version Honda Ridgeline? If so you should go with a couple of
SportRack ABR511 J-Stacker kayak racks. They are cheap but work wonders. They will install onto the factory crossbars no problem. No extra factory rack adaptors or anything needed. The thing that's cool about the SportRack ABR511 kayak carriers and all other j-cradle style kayak racks is that they carry the kayak cradled on its side. That means you use up much less crossbar space than other kayak racks that carry the kayak flat. This is especially important on most factory racks because you can carry two kayaks using 2 sets of j-cradle style kayak racks. You have plenty of clearance to access your Honda Ridgeline truckbed as well.