Last year I installed a Matris fork kit and rear shock. When Matris custom makes a shock for you they have a range of adjustment that they allow. That adjustment at the shock is 10mm. I am not positive but believe that work out to be around 1 inch in actual height.
You can spec the rage to fall within your target. I told then to make the shock center of adjustment to be the same as stock length so I could go up or down a little. I want the bike a little lower I thought but at anything lower then stock length the ride suffers and gets harsh by a small margin. Once you get to stock height setting everything smooths out.
I mention this for those wanting to lower the bike with a lower shock, be prepared the ride may suffer. There may be a reason for this with the linkage setup that a mechanical engineer could explain but that is way above my pay grade.
I even re-greased the link roller bushings thinking that may help.