All the manufacturing in the world they must install those with screw anything that attached to the car body spoiler , side skirt , front .. only the owners for the C5 they like to install these things without any screw ? If you buy the spoiler that's means you like it so why you don't screw it unless if you're going to change it every year
... I don't think it's a good day when you driving and the spoiler fly ... just do it right .. screw it and drive safe ...
By the way the manufacturer they say in instruction we are highly recommend to use the screw for safety reason ..
C6 have screw
C7 have screw
C8 have screw