I would recommend 20%, if it is legal. Kinda dark at night, but tolerable. 35% is too light during the day.

I had my g/f's 05 Accord LXSE tinted with 30%. Not quite dark enough, but okay.

I had my non-Honda tinted with 15% sides, 30% tint on the back window, and 30% strip on windshield. The 15% kinda sucks at night, but I wanted 20%, which was not available. The 30% on the back was to make backing up at night easier, and to have my car semi-legal in CO.