Window tint suggestions...

So I got my windows tinted yesterday. On the recommendation of the shop owner, I went with 5% VLT tint on the rear three windows of my car, and 50% on the front two side windows. After some consideration, I think the 5% is too dark. It makes it hard to see cars very well through the rear view mirror. Let me clarify that a little. I can't tell if cars behind me are cops, or not. That's kind of a problem when I'm going a hundred miles an hour, passing freeway traffic like it's standing still. When I get a certain amount past a big group of cars, I get a liiitle paranoid about who is behind me, and now I can't tell very well. :(
Must... slow... down...

I think 20% would have been better for visibility's sake, but damn does it look good on the outside. White cars with tint look gooooood...