if it helps, the trim around the windows are also a factor. personally i have a base model no gloss shadowline trim for me so going too dark doesnt look appealing imo. like rexg, i have the same so 35 all around is good . if you have the sportline and the trim is shiny, then go as dark as you can. itll help bring out the bling on the car.
ps dont forget the rim color as well.. THAT right there should be the the biggest determining factor
the only thing in this world that gives orders is balls. You got that? Balls.