There are 2 types of Wind Deflector for Z3 without Roll Bars, I have heard the 1st design cannot be folded when the top is up and the 2nd design is hard to install. What I really wanna know is will I lose any storage space in the rear compartment if I install any one of them. which one has a better wind blocking ability? how is the rear visiblity for the 1st design when the top is up?