Mounting Rhino Rack J Cradle (kayak rack) to Prinsu Crossbars??

The Rhino Rack J Cradle (folding) comes with clamp plate + knob nut mounting hardware, which doesn't work on the new Prinsu crossbars because of the clearance between the bars and the body of the topper.

The new Prinsu crossbars are smooth on the bottom, which require these new Prinsu L bracket mounts...the result of that is the Prinsu rack sits lower; there is less clearance between the crossbar and the body of the truck (in my case, the topper).

I am looking for a way to mount these J Cradles directly to the crossbar in the provided channels, but the holes in the J Cradle do not line up with the Prinsu channels. I've looked everywhere for a mounting bracket or plate that I could mount to the Prinsu crossbars and then mount the Rhino Rack J Cradles to the plate, but I can't find anything. Has anyone ever mounted a Rhino Rack J Cradle kayak carrier onto their Prinsu crossbars using the crossbar slots and channels?