I've been looking at replacing the bushings on my coffin arms also. Powerflex has bushings with two different 'hardness' - track and street. If you do this I would be interested in what you think.
I'm delaying doing this because I am also considering changing the entire arm from vertex auto. This 'upgraded' arm has a replaceable ball joint.
Porsche Boxster Control Arms Upgraded & Rebuilt | Vertex Automotive
I recently replaced my rear upper control arms and it made a huge difference and got rid of a lot of noise. I'm doing the front upper control arms tomorrow.
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