Keeping the front windows legal will help though. They have to be able to actually MEASURE the light transmittance through the window. Which they can't do (to my knowledge) without having acess to both sides of the window at the same time. The little gauge they use slips over the edge of the window. That is something they can't accomplish on the rear windows of a mustang with their little handheld gauge. Unless it's a vert of course.