When installing the sensors on a car, how do you best determine where they aim during installation? You can't just use the bubble balance supplied with the kit because it doesn't account for whether the car is sitting level on the ground. For that matter, how do you determine what on your car is level to use as a guide?
Most cars do not have some location that is exactly level when the car is sitting on perfectly level ground. I think finding perfectly level ground would be quite a task as well. You would need something perfectly straight that's longer than the car's wheelbase, place it on the ground and put a level on it to verify. Then, find something on the car that matches (is also level).
Since the sensor produces a "cone of light" (as in "divergence") that grows as the distance increases, is it enough to get the sensors relatively straight and level but not perfectly level? This is what I've done on my installation. I'm assuming there's a margin for error.
Also, is it better to have them pointing up slightly so you don't waste some of the light pattern hitting the ground? This seems prudent but then on the other hand, what if you're cresting a hill? It seems to me you would want that coverage in such a situation.