You should check your state law on tint. Most states are 35% to 30% max on the front side windows. All your rear 1/4 windows and back windshield can be as dark as u want. U could black them out with paint if wanted. I usually do 5% on all the rear windows..
Very very few states have no tint laws but most states do and are pretty strict. FYI, if u are ever caught with your full windshield tinted by a State Police officer, they can impound your car! And write u a ticket. Its also dangerous at night..
I know in most states with tint laws , State troopers carry a meter to check your tint.. They could make u strip it right there or write u a ticket or both.. Its considered unsafe to have it darker then the state tint limit. Also, u could fail inspection. I know here the inspection stations have meters too and are supposed to check it as part of the inspection.
IMO- go 5% on all back windows or atleast the back windshield.