This might explain it better.I happened to have a 5mm thick steel spacer that fit exactly in my bin of parts lying around. The stock mount is liquid filled and is very soft. The Z1 is a good stiffness but the bushings are squashed too much so even without any load on the mount a lot of NVH gets transmitted. By reducing the amount of squash the mount is allowed to move slightly when under slight load but is still 100x stiffer than stock when at max load and will probably never go bad. The modification is internal so its not visible at all. The Z1 mount in the pics is before modification, basically the lowest part of the mount will be 5mm lower to relieve some preload. This does not change the mounting height of the mount so driveline geometry is unchanged.
