I recently picked up a used Zumo 660 with a Touratech locking mount. The included Ram hardware seemed wimpy and wasn't very secure. I saw the mounting bar BMW uses on the newer GS and decided to try that option instead.

I like the fact it puts the GPS above the instruments. There's also room left for adding other small farkles if needed.

The bar is simple to mount, no additional hardware was required. But pulling out the instrument/headlight cluster made it much easier. I also took off the windshield but it's not really necessary.

Attaching the Touratech mount did require longer bolts. Apparently their clamps were intended for a smaller diameter bar. I used these 3/16" carriage bolts that are 1" long with 10-24 nyloc nuts. These are a pretty close substitute for the 5mm screws supplied by Touratech.
The final result is a rock solid mount and the Garmin is just a glance away.
Cost of the mounting bar was about $60 for part number 71 60 7 707 369.
_Rex