The Garmin computer is still very stable on the mount even though it looks narrow. If you criss-cross the O-ring bands per the Helpful tips sheet and the rubber mount you are using, you should be good! Let me know if you are still having issues after you try the tape method.
Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike
Candice Turner
CEO
XLAB - Aerodynamic Triathlon Accessories
Dawn to Dusk - Off-road Specific Storage Accessories
http://www.XLAB-USA.com http://www.dawntodusk.bike