After much consideration ended up joining Garmin wires to rear of front power socket.
Garmin supply box just fits on top of the rh tank tongue near headlight bulb. I used sticky backed velcro.
all wires tucked under clocks on top of headlamps.
Bought a great hi-level bracket from engimoto.it
all done and dusted.
there's a great video on YouTube showing how to remove body panels on 1200 multi.
all sounds simple - took me all day