Mine is just behind the toolbox, just sitting there. Nothing holding it in place because where could it really go? The only downside of mounting it that far toward the rear of the bike is that six foot cables barely make it forward to things like the GPG, Push To Talk switch, the GMRS (or however you arrange those letters) tranciever to talk with other bikes, etc. But the mounting place itself is great- take off the back seat along (I have a two piece Corbin) and it is very easy to service.
I also have a remote control mounted in the glove box so I can adjust the unit without having to stop, get the passenger off and pull the rear saddle to get to the controls.
Brian
Where did everyone put theres? saw one tread were they mounted it under the left dash.