Hi Shaun:
I also use the Garmin mounting kit - you can see it at the link posted above, or directly on the Garmin website at this link:
Garmin Moto Mount for 26xx, 27xx, and BMW Nav II. I'm very happy with it, have used it with a 2650 and a 2720 for over 50,000 km now, it's still good as new. The Garmin mount has a built-in clip for holding the power cable after you remove the GPSR from the mount, and it is also very low-key - Garmin was smart enough not to put their name on it in any visible location, and not to put "PRESS HERE TO STEAL GPSR" in big letters on the front of it, like one of the aftermarket mounts (Doh...

).
As far as WHERE to mount it is concerned - that depends a lot on how old you are (seriously, no kidding). Between 40 and 45 years of age, the muscles inside our eyes start to lose their elasticity, and it becomes more difficult to rapidly change from looking at infinity (where we normally look when we are riding) to looking at something very close to us (like a map or GPSR). So, if you are close to that age range - or, like me, above that age range - you might want to try to mount the GPSR so that you maximize the distance from the GPSR screen to your eyes. This will make it a lot easier to quickly look at the GPSR, and quickly refocus on it.
If you wear bifocals or reading glasses, have a talk with your dispensing optician and find out what distance the lower portion of the lens has been optomized for. I think (I am not sure) it is typically about 60 cm or so. Whatever that distance is, that is what you should try to target from your eye to the GPSR when you mount the GPSR. If the GPSR is significantly closer than that, you might need to get a second pair of corrective lenses just for the moto/GPSR - and that can be a pain.
I have four different sets of corrective lenses - one for normal stuff, one for flying a certain model of plane that has the instruments about 90 cm away from me (a longer distance than normal), and one that is set for 150 cm away, which is the distance from the instructor station to the aircraft instruments when I am teaching students in a large flight simulator. The fourth set is for reading the map on my tankbag, which is just too darn close to me (about 14 inches away) to comfortably focus on it when I am on the bike. Because of the PITA factor, I try to avoid using my tankbag to hold the map.
Michael