Somewhere there's a great thread about blind spots, but dipped if I could find it right off.
What works best for me, is a new perspective on positioning my mirrors.
Basically, The instant the car behind me is no longer visible, it's front bumper should emerge in my sideview mirror, in my periferal vision, looking ahead.
Seeing down the side of my short smart is of no use, although it does take getting used to until you trust.
I'm ordering a wide-angle addition to my rear-view mirror, which should, as it did in my Subie, help inhance my periferal vision.
Remember, we're only 8 feet long, and from the mirrors to the rear? I'm going to go measure.

.....................................girl y measuring tape
Ok. 70 inches. That's 5.83 feet, call it 6.
So, could two somebodys measure the distance from when your helper dummy 'car' last appears in your rear-view mirror, and appears in your side view mirror? My thinking is, that if we know, physically and precisely, how far a thing is behind us, and see it in relationship to our mirrors, in a dry setting, then we can better learn the tools of rear-view mirrors to use their best advantage.
Grandpa's taking a nap. We can do it tomorrow. <big grin>