I use a trunk bag and panniers. I've mounted my DiNotte taillight on my rack, using the standard O-ring that comes in the box. You just have to wrap around the twice to take up the length.
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Nice set-up. I am toying with making a bracket to attach to the rack to hold it ---- possibly under the rack. I want some fool-proof way of insuring it points at the correct vertical/horizontal angles all the time.
It apparently has an 18-deg cone best I can find out so far. I assume that's the angle between the half brightness points as is typical for these kind of data. That's very roughly 27' (+/- 13.5') at 100'. However, I've been in a bumper to bumper situation where the vehicle in front of me makes a sudden move to pass or turn and here's a poor cyclist right in front of me that I couldn't see until the big SUV moved.
That 18-deg cone becomes only about +/- 3.4' at 25 feet.
Al