I have 20% all round, (Factory 20% in back) It's fairly dark on the inside when it's day. But I can still see outside when it's night (But not very well)

That's the biggest problem with tint any lower than 20%. If You're doing a lot of night driving (And A lot of backing up) I wouldn't reccomend any lower than 20%. Most people can see in the cab (in the day) A little bit with 20, but hard to tell who's inside. silhouette's if you will.

 

you dont have to tint back if ya got one of these, its called windowscape..they come in all sorts of designs....