Short answer is we have applications that are real low and some that are a little higher. It all depends on the specific vehicle.
Our goal is to have the light as low on the post as possible. Our engineers examine the vehicle and choose the lowest spot that doesn't compromise function or safety. The one exception to this is police vehicles like the ones you posted. We work with Ford, Chrysler, and GM for spotlight applications. They decide where they want the light and we figure out how to make it fit where they want it.