Regarding the short shock CG difference I did a quick estimate and if you can get that entire 40gm mass 4mm lower it would lower the CG of the car by approximately .1mm or in percentage terms .3% lower.

For most of us that would be negligable. For a top tier driver though it may provide that .05 sec they need to win. As an overall guide get everything as low as possible and get the track as wide as the rules will allow. That will minimize the Lateral Load Transfer and allow the chassis to develop the maximum grip from the tires.

I have to agree you both though for most of us it would be a negligable difference as our driving is not consistent enough to take advantage of such a small change. You would be better off focusing on getting a good driveable setup on your car and then practice practice practice to get the consistency.