I'm in the process of making an aluminum rack to (occasionally) add to my 'Genuine Kawasaki Rack' that I recently put onto my '15 for just this purpose. The rack mirrors what I had on the GREEN HORNET for carrying the tent, sleeping-bag, etc I carry on long trips such as D2D.
When I got home w/ the 20" x 24" piece and laid it onto the rack, I saw that the stock tail-lights are rather 'hidden', then on removing the aluminum piece and looking AGAIN, discovered that the tail-lights are pretty much hidden w, JUST the Kawi rack on....
Got back on the GREEN HORNET TOO, and 'toodled' down to Princess Auto to see what they had for LED lights. After about 45 minutes comparing them I decided to get this:
then rode by the place where I got the aluminum, and picked up a foot-long piece of aluminum angle, 1" x 1".
I spent half an hour measuring, then determined I could cut it to about the same 9 5/8" as the light,
Next I looked at the wiring diagram, determined that the brake light is powered by a blue/red-trace wire which I 'tapped' into, running the ground to a convenient bolt at the rear of the seat pan area, drilled two 1/4" holes into the Kawi rack lower piece, 'rattle-canned' the aluminum angle black and mounted it to the rear of the Kawi rack.
and here's what it looks like.
Here's w/ running lights
and brakes ON.
FWIW - light cost $25CDN (tax in.); paint, wire, tape, connectors maybe $2; aluminum angle free.
I SUGGEST that you w/ Gen 3s take a GOOD look at your visibility from the rear.