In a recent discussion bar extenders were mentioned. While searching for something else today I found this Yakima bar extender.
Both Yakima and thule have them. It can be very helpful loading a boat onto jbars with one. Put the one end on bar pick up other end of kayak and up she goes. Of course if you have Yakima bars you need that one if you have square thule bars then the one from thule.
Have had the Yakima version for years. Almost a necessity with their J racks.