get a couple of spare parking lamp or turn signal twist lock holders and 3 or 5 bulbs. Then drill out the corner blanking pieces you see and use a small file to make the locking tab slots - all the moulding marks to cut are on the plastic housing itself, you will see what Im talking about.
wire up the bulb holders to the parking light circuit of the tail lights - it will make the whole tail lamp light up evenly and also would be seen from the side of the car.
The early Khybers had the bulb holder actually taped to the wiring and just tucked away - the later ones were completely missing that - easy job to install.