I personally wouldn't go as dark as 5%, but that's just me. I like to be able to see out my windows at night. Especially when backing up. Billy has i think 20% all around on his WRX and that car gets really dark at night. I wouldn't go much lower than that.

 

Yup, 20% in the WRX seems to get a bit darker then I like at times. More so then any of my other vehicles and this is the lightest tint I've had so far.