Not sure which 'subforum' in accessories this would go into, since it's applicable to a variety of gadget mounts...
I dug around on the forums a bit before tackling my XM installation, and I don't believe I saw the method I used, so I'll post it here. It took me all of an hour, including taking the pictures, and it turned out pretty clean.
RoadyHolder, offset right (BMW clutch version), $34, www.hoonhardware.com
XSOReeKey voltage converter (can't remember cost, bought it a long time ago), www.2wheelinnovations.com
(think they're out of business, but hoon has an eqivalent power supply for about $30.
Female spade crimp terminals, .110" width
What I hadn't seen before is someone tapping power from a connector I found inside the left handlebar plastic. My '03 LTC has the ComSystem with a PTT button under the left grip, and this connector was a breakout from that harness lead (see first photo below). Anyone know what this connector is normally for? It was just tucked under the handlebar, nothing connected.
I probed the three pins and found black to be ground, white to be dead, and red to be 12VDC switched to the ignition key. I bought the female spade terminals, which fit nicely into the connector housing.
Then I tucked all 600' of wire into the lower handlebar plastic, secured with a few Ty-raps, and was still able to get the upper piece back on with no trouble. I really like having the antenna wire tucked away, rather than bundled up on the back of the RoadyHolder bracket like HoonHardware suggests.
I use the over-the-air FM transmission for the audio hookup - I don't do much cross country travel, so I don't need to worry 'bout the direct FM antenna connection.
Now, if I could just get the iPod hooked up as nicely, I'd be set...