I used an MV Motorrad ram-mount ball that screws into the threaded hole at the center of the handlebars. http://www.mv-motorrad.de/cosmoshop/...119463251,.htm
The BMW badge comes off without tools — just push down on one side and pry up the other side with your bare fingers. The MV ball screws right in, and looks factory fresh.
The Zumo included a ram-ball that screwed into the back of the cradle, and a short RAM arm that connects the cradle with the handlebar mount. It is a little bulky — the Zumo itself is thicker than I expected, the cradle is equally thick, and then the arm — but it looks great from the rider's view, which in the end is what matters most. And it is solid — there's a new security screw that ensures that the Zumo won't zoom off your bike.
Of course, the downside of any ram-mount configuration is that anyone can simply turn the wingnut knob and walk off with your GPS and cradle. I'm looking into a knob with a lock that replaces the wingnut — here's a link: http://www.whitehorsepress.com/popup_image.php?pID=5542
I'd like a cleaner mount at some point — perhaps scrapping the RAM mount entirely and screwing a threaded techmount in the center of the handlebars. But considering the girth of the GPS and cradle, it might not make much difference.
I've been through several GPSes already trying to find one I like — the Nav III, the Nuvi 360 and now the Zumo. The Nav III was mounted too low and was too clunky for my taste. The Nuvi was sleek as can be, but lacked too many features: no Bluetooth for voice prompts; its screen wasn't excessively bright; limited to one via point. The Zumo seems like a good compromise — full-featured, portable, waterproof, Bluetooth voice prompts, bright screen . . .
I purchased the Zumo from getfeetwet.com. The price was right, and they allow you to trade up anytime within a year in exchange for a 15 percent restocking fee. Pretty good deal for someone as flaky as I am.
Questions? Fire away.