I bought this as an upgrade since we bought the Toyota Sequoia which is wider than my older Mercedes GL. I also ordered the Thule Outrigger which works nicely with the cross bar to load and unload our SUPs easier. The combination works very well. I offer a suggestion I did which also worked well with me. If you want kayaks or boards to roll easily over the cross bars and without scratching try this: Go to Home Depot and buy two 30-40" long (depending on the width of the car top) of 1.5" diameter PVC pipes and two-2" pipes of the same length. The 1.5" will fit inside the 2" pipe nicely and the cross bar will fit into the combination (through the 1.5" of course) very well. This will give you a very nice set of rollers for the two cross bars and if you buy the black color of pipes they will look very professional at a cost of less than $15. I tried so many commercial covers and rollers and nothing worked better than this home made one.
I can't comment on J carriers because I don't use them, but perhaps I should. The design weakness with Thule is the square bars, which only becomes a problem on curved roofs, but as the roof curves so must cradles cant away from each other, reducing contact between boat hull and cradle to inside edges. The cradle faces are absurdly small to start with; this rotational deviation from level makes it even smaller. Couple that with Thule's comically inadequate détente angle fixing clamp (for holding the saddle in the shape of your boat hull) and for support you are probably better off using foam blocks. So J carriers may work better on a curved roof, if I can lift that high. I've seen some people use them for composite boats so it might be OK.
Choose aerodynamic roof bars for superior performance and a sleek, sophisticated look that complements the lines of your car. These roof rack cross bars also have many smart design features. A textured surface disturbs the airflow and greatly reduces wind noise. The aluminium extrusion creates one of the strongest load bars in the market. The design gives you quick, no-hassle installation. While the end cap pivots and T-track make it easy to add further loading options.