I would be careful not to go too dark. I have 50% rear side and 75% rear. I did have 25% on the fronts but it was too dark in anything other than sunny conditions.
At night with the 75% rear window at night all you can see is lights and not much else. Difficult to see who/what is behind you. Could find yourself in a situation like this...https://www.gtr.co.uk/forum/301097-oh-sh-t.html