On my old truck I had 20% on the windshield with a 5% strip over that at the top, 5% on the sides, and 5 over double 20 on the back 3.... very dark indeed. Was great to drive in the day (eyes are very light sensitive), and wasnt as bad as you would think at night. Often required rolling down the windows to backup, but a little fore thought of how to get out makes it easier. Only time the windshield sucks is on a back road at night when its raining and there is oncoming traffic so you cant use your high beams.
I had 35% at first on the windshield but that wasnt dark enough for me so I went 20% with the strip. Never got hasseled about the windshield (although one cop made a comment about it), but did a few times for the side windows. The strip really makes it look lighter. Tint may have been my favorite part of that truck haha.