I put the coupe springs on the rear so it would sit a bit higher than with the z springs. If you look at the measurements in the post you can see exactly how much. I did not like the way the car looked lower in the rear with z springs. The easy fix was to install coupe springs and now it sits perfect in my opinion.

Others like it with z springs all around. It just depends on what you like. As far as I know, all z springs are the same height. I am pretty sure I would have wanted to change the rear springs even if I had used 06 z springs.