your front will be pushing it. i'm on a 17x8et28 and i do have more than 5mm to spare. but your 18" will make a big difference
in the rear, i run max -camber and it tucks the lip riiight behind the fender when i'm air'd out. if i'm low enough while driving, it'll rub the lip of the wheel on the inside of the fender when i squat or turn. your 8"et27 will be fine with some camber adjusting.