I use 5% brow, 20% front roll ups and 5% rear roll ups and rear. It actually blends better then you might think and when backing up in a dark parking lot being able to see a "little" out the window in the mirror is better then none like 5% in the front roll ups I have done before, especially in the winter. I would say if you are in the city and have nice lit roads and parking lots go for it with 5%. More rual area you might wanna consider 20% for the front roll ups.
Just my .02 though