50% is legal.
I did 50% on my accords front windows and 35 on the rears. you can barely tell the fronts are done I will be going back to get 35 done on the fronts. I was afraid of getting pulled over with a black car in gahanna and working in new albany. I only got hasseled once or twice with 5% on the SRT4, would do that again with no issues.