Like Nick, I think you have them set too soft and the suspension is bottoming out all too easy / quickly, especially as it's already quite low now.
Try turning them up by about 1/3 to 1/2.
But (and your probably not going to like this!) if you do want a better ride, raise the car up - even just to try it, you can always lower it again.
Interesting......but the rear design does not have a bumpstop, correct? The suspension is not bottoming out (like from a rolling dip) - its the small things in the road (like 10mm thick reflector) that transmits LOUDLY on the rear. Like these things pictured below - when I clip them with my 10" tires/wheels, its like BANG BANG BANG (when I run over a few). Also with pavement patches (not potholes) are really loud on the rear. Mind you, I only have a mild suspension upgrade...I am using GAZ lowered shocks and maybe my car sits a tad low, but not sure on how it would change by raising it to "soften" the ride over those small imperfections on the road. Again, I do not think I am bottoming out....I think that would require me to hit a small dip in the road and when suspension compresses severely and would go BOOM (meaning bottom out)
Edited by thebluepotato, 07 May 2018 - 08:44 PM.