Here are some pictures and basic explanation of where my mechanic friend, Capn Kneedragger, wired up a Centech AP2 and its wiring harness, APR130r onto my 2009 R1200RT. The short and sweet on this is:
All that needs to be removed to install the Centech by this method is the passenger seat and rider seat. If you have heated seats, you will also have to disconnect them; each seat has its own separate wire, and the disconnect can be done relatively simply by pinching the clip and pulling away.
1. The AP2 is mounted sideways on the rear fender, beneath where the passenger seat abuts to the rider seat. A sideways mount allows both sides of the AP2 to be accessed easily to wire up gadgets. The wires into the AP2 come into it from the side that is nearest the rear of the bike, b/c that seemed to be the best way to keep the wires neat and separated from each other, and also, not shoved up against the crossbar in the frame. Wires were soldered and heat shrunk. This placement does not interfere with anything, including the OEM BMW tool kit, which can be seen in place. However, in a reply to this thread, Racer7 says this placement may interfere should anyone wish to use an Ohlin shock, so the fix is to mount the AP2 a few inches further toward the back. See Picture 1 below, which shows both the AP2 (on right) and the relay switch (mounted to the crossbar; closeup picture of that to follow) and lots of zip ties in place.
2. The relay is mounted to the crossbar using the screw hole that already is in the bar. We also used a zip tie for extra security. See picture 1 below. But a close up of the mounted relay will follow in a second post.
3. The orange wire (the relay trigger) is wired to the wiring for the rear accessory socket. This was the only one that could not be heat shrunk. One option, which we did not use, but which would be much cleaner than going directly to the wire was to buy BMW's pigtail that can be plugged into the accessory socket from inside and under the seat (ie, we're not talking about the male pigtail that you can plug into the socket as one would use to plug up a charger, etc).
We also opted not to use any extra clamping diodes, although that is probably the safest way (as my mechanic friend agreed with Racer7 and Deilenberger from this forum on that point). I made the decision not to use them based on the experience of several of my other friends and some posters on this list who have not experienced any problems by going through the accessory socket.
Capn Kneedragger also used the voltage meter to check everything as he went along and when we had everything all wired up and used a lot of zip ties to keep wiring securely in place.