lol even preloaded they can clunk. THe problem isn't exactly with the coilovers I have noticed, but instead with the lack of a bushing for the upper shock mounting plate.

The upper plate on the rear is just that big metal circle.

If you think about it, since it is only mounted with two nuts, it can rock side to side parallel with those two nuts.

Since there is no rubber bushing or plastic bushings between the plating and the shock, it clunks slightly. I had this same issue. I don't think there is anything you can do about it.

If you really notice it that much I guess you could try putting a rubber circle peice between the shock upper plate and the chassis.