Just wondering if you have tried actually loading a sea kayak on J-bars - or saddles, rollers or stackers.
The reason I ask is that loading, especially if solo, can be a good bit easier or harder depending on the type of support and the specifics of the car. It is not correct that J-bars are always easier, something car salesmen tend to spout who don't actually paddle themselves. I think they do generate more money for the dealership though.
We have a good little collection of rollers and saddles, which might someday have a use again but for the moment sit in the basement. We tried them out and eventually found that the older style stackers worked better for us. It is worth messing around with your boat and the various systems if you can find some willing paddling friends before investing your money.