Blocking the rear window would likely be overlooked by FHP due to side mirrors. If driver's side window or front passngr window was blocked, or heavily tinted, that would draw police attention - or windshield below a few inches from the top. Remember, from someone who has driven coach and tractor trailer, not all vehicles have rear windows. True, a passngr car is regarded differently, but police are busy with important things; the side mirrors would likely earn him a pass.
Good point.