Last weekend I got these mounted on my 2012. I used SW Motech light brackets, and designed a custom wiring harness for the task. The harness uses two heatsunk Schottky diodes, two relays, and a three-position SPDT switch (on-off-on) for mode control. It's all wrapped in a big fat heat shrink tube (sans the heatsinks). Signalling power is tapped from the forward/headlight side of the bike's wiring via Posi-Tap connectors (so, I didn't tap into the actual bike wiring harness). The taps are inside heat shrink tubing. The relays are mounted via zipties behind the speedometer/display. All the wiring I used was marine grade stuff from West Marine, as was the switch I used.
The three modes are:
(1) Switch off: lights behave as per stock, D2 lights not used.
(2) Switch on left: lights behave as per stock, D2 lights are on with high beams.
(3) Switch on right: low beams are completely replaced with D2 lights, high beams behave as per stock.
The motivation for mode (3) is power savings: the D2 lights use about 20 watts, while the headlights use quite a bit more. This mode of operation is definitely not street legal.
Because I run Skene Design P3 tail lights along with a well lit top box, I can now pull the stock tail light bulb and switch to mode (3) to make available almost 100 extra watts of power.
The stock lights (high and low beams) are nothing short of pathetic in comparison to the D2s. There is no situation I can think of where I would want low beams on with the D2s.
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Highbeams only (for comparison, all pictures taken within 2 minutes of eachother):
Highbeams with D2s:
Left side mounting: