I don't want to hijack this thread, but another possible reason for your continued shimmy is the center/drag link. I recently replaced the one on my S600 Coupe and the one in my 500SEL a few months before I sold it. Once I did that the shimmy in each car was gone. I had also replaced the upper control arm on one side of the 500SEL, but that did not correct the shimmy. The drag links each had a totally loose "ball joint type" fitting. That loss of stiffness, etc. allowed the wheel on the right (passenger) side of car to oscillate at some frequency, depending on speed, which was the shimmy being felt at the steering wheel. The link in the coupe was so bad that a slight shimmy was noticeable at very low speeds. The tires had recently been rotated and balanced, so I didn't feel they were the problem.
The drag link is very easy to replace and installing a new steering damper at the same time would help with the overall performance of the steering. The damper attaches to the drag link on one end and the car on the other. The drag link attaches to the the idler arm on one end and the steering gear control/pitman arm on the other. I needed to use a puller to get the ends of drag link out. Not a big problem but I had access to a lift rack so it was very easy to reach all of these fittings. I am sure others here have done this in their garage, most likely using ramps to elevate the front of the car to gain easier access to the drag link ends.
Just an idea. Hope this helps.