I feel my car sits a little too low at the rear - another 1/2" of height may well be all it needs to both look OK and help with ground clearance. Is it possible to add a spacer to the rear upper or lower spring seats? The EPC lists only 1 version of the upper seat for the 900 but for the 9-3 it lists 2 extra versions for 16" and 17" wheels. Do these change the ride height or is it just the length of the bump stop?