I have no idea how the percentages work.
I had 35% on my black G6 and hated it cuz it was so light. But anything lighter than 35% and your pretty much waisting your $. So like silvaman said...suck it up
I'd swing in to a tint shop or the place your gonna use and ask them. They might have samples for you to look at also. IMO thats the best way to tell what your gonna like. And the people installing will know the rules ect.