I just had the two point, always tempted to try the K brace though.
I’ve noticed no ill effects, it’s very easy to fit and remove. When you look under and see the design it’s little wonder there’s flex, brace works for me :)
The steeda lower G track brace is the best thing I’ve done to mine, noticed an instant improvement in turn in, I did the strut tower brace shortly after and I’m not sure it did anything, apart from look pretty……but it can’t hurt :like:
I had this too and it was driving me mad, window would go up and down when driving! I removed the door card and pulled all the plugs, made sure all pins were pushed into each plug fully, put everything back together and it’s been fine since, so obviously had a poor connection somewhere!
Not sure why that would make a difference to the rear 1/4 and door, but It is the most relevant S550 to me though, and the body is the same no matter what one you have.
I see it anyway, and I’m not alone lol