Don't know what the laws are there in your area, but in California it's a "no-no" to tint the driver or front passenger side windows. Anything rearward is ok to tint. I've had two (4-door) Mercedes tinted with 50% on the four windows and 35% on the rear. Haven't been stopped for tinted windows, although I've rolled my front windows down many times prior to passing a CHP sitting on the side of the road
. Personally, I think the 50% is a good compromise on looks, performance (sun block), and safety (not too dark, especially when night visibility is critical). Remember, an outside observer will be looking through 2 sets of tint, so it'll look darker to them than a person on the inside. This is especially true if you have a dark interior, then it'll really look dark to an outsider.