On my BMW e23 7 series, I had to create my own custom coilover since they don't offer anything for that car. Anyways, here's a picture of that same top perch being used with the stock "guide support." I am sure same principal applies to the x5.
Since the 4.8is has stock air bags in the front, I think if we wanted to get rid of the BC front camber plates, we would also need to buy the stock guide supports from a non-air e53.
Here's a diagram from a 2005 4.4i with non-airbags. You would need (2) #1s (31306779604). I am surprised the price is actually pretty reasonable. Although you lose the adjustability of the camber plates, the stock guide supports should be quiet and more comfortable.
ECSTuning ($42 each for Lemforder)
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