That's what I've adopted: flashing low on the Carback radar hung under my seat with a steady red high on the back of my helmet.

There are steep hills where I live and ride so I'm hoping that high red is the first thing drivers approaching from behind will see as they come over a hilltop I've just crested, then the blinking red lower down the closer they get.

99.9% of the vehicles passing me tend to move well to my left as they pass. The 20% who move into the oncoming traffic lane give me the heebies when they're entirely over the double yellow with no possible way to tell if there's something coming up over the hill in front of us both but in that lane.