I have the i-600 mounted in my 'Busa tucked behind the right turn signal "pod". I have it zip-tied to the subframe horizontally. The rear end plastic comes off super easy, and in one piece.
I chose to place it there, as one of the first places a thief may look is under the seat (battery). It's out of the way, and close to the rear turn signal harness for a nice clean, and inconspicuous install.
You could also pull the nose and stuff it anywhere you wanted, there is plenty of room up there.
I just installed an i-900 on my Concours-14, and pretty much used the same ideas. The only difference is that you should keep the RFID antennae as far as practical from any source of RF interference. The antannae on the i-600 is more forgiving, but the range will probably be reduced if you route it along a metal support like I chose to.
One side note: The battery life in the remote is not all that great. Remember to keep the remote charged. Like a cell phone, the more interference the remote encounters, the shorter the battery life. When feasible, I will arm the alarm, and turn the remote off. The battery will last longer, especially on a longer ride where you will be arming/disarming the system, and using the pager feature. The downside is that if someone was to tamper with the bike, I wouldn't get the benefit of having the remote notify me. The work-around? Simple, layers of security, and whenever possible, park it where you can see it.