I use the pro-fit bracket (formerly used with my full-install car kit) to support my pro-clip holder. The two made a very good combination for my 7290 in my Toyota Highlander. I'm waiting for the new 8700 holder to arrive.
They have brackets for most cars, including BMWs. Check this site and look for VSM (vehicle specific mounts).
www.pro-fit-intl.com
Yes, I do get some GSM "buzz" over the radio, but you will probably find that anytime you put a Blackberry near the radio.