My thought was to have something that was clearly a brake light, even if people didn't see it come on. I've had several people in the past mistake the original corner brake lights (on my old TR3A) for tail lights.
This seems to have been effective. I've noticed that people are more apt to stop a bit farther back, rather than running up until I disappear under their hood ornament! The video below also shows my LED tail/brake/turn on the left, with a tungsten bulb on the right. Not a huge difference, but I like how the LEDs come on just a tiny bit sooner than the incandescent.
[video=youtube;q4GMcD9DktQ]https://www.youtube.com/watch?feature=player_embedded&v=q4GMcD9DktQ[/video]