I have 5% all around in Vegas. Its illegal and very unsafe to tint the windshield, just buy a nice pair of sunglasses and you will look better too. Never had any problem with the Cops since Iam in a place where the sun is the brightest.
what will look nice will be trouble free for your car will be 5% on the back and 20% on the front windows. Coupes are actualy darker inside than Sedans so you will be OK will a 5/20 tint. GOODLUCK