For a longer sea kayak or recreational boat, I would recommend the Yakima Mako Saddles. The J-bars are great for small whitewate boats, but from topping 2 sea/rec kayaks on a smaller 4X4 Ford Ranger pickup, we have found that the shape of the boat tends to make the vehicle pull to the direction the bow points. If on its side with J-bars, it will pull left or right unless you have a pair of kayaks facing into or away from each other.
We mount ours upside down as the deck is more rigid than the hull (heavier rotomolded boats - fiberglass or composite is much lighter and stiffer). It also allows the boat to push down and prevents rain getting in even in a downpour. There is NO deformation of the deck or hull. We do use cockpit covers also. On the pickup, the bars are 5.5 feet apart, so with 13'-14' boats, we do not use front or rear tie downs as only 4' is out on each end. The racks are removable with permanent mounting brackets. We use 4 safety straps under the actual bars in addition to the saddle straps. This setup has been on multiple 600 mile trips and has never loosened, moved or slipped.
I have found upsiode down is more stable in the wind at highway speeds, although a sharper turn at speed will feel like the vehicle want to go straight...
I was going to mount the rack to the Santa Fe, but do not feel the SF rails seem as durable, so we are going to get a hitch and trailer them which allows us to fill the boats with the paddles, vests, and other light but bulky gear since the Santa Fe cannot carry the volume of gear the Ranger does. Plus it is more aerodynamic. We have found the boats cost about 1.5 MPG at 70MPH, so we are still over 21 MPG on the highway with the truck. Since our SF is getting 25-26MPG over the road, I do not see a trailer with the kayaks in the slip stream having much effect.
ALso, be careful when opening the rear hatch as a longer boat may hit with a roof mount (that too figured in our hitch decision). Good luck however you go.