Another recent discovery:
If you notice, the set up requires two positive inputs (grey & blue/yellow) and one ground (white/black). I've found that if you pop out the middle vent piece, you'll notice that there are four wires going to the clock. One is green. Forget that one. The other three, however, are white/black (ground), grey (15A Cig/radio), and blue/yellow (20A dome). The grey you don't have to worry about since that's coming from the switch, which is already wired in the USDM cars. But for the white/black and blue/yellow, the clock is a great place to splice the connections to the relay. If you get some of those wire tap-ins available at radioshack
just splice from the blue/yellow and white/black wires on the rear of the clock and you can probably also stick the relay back there. There's enough space for it. I haven't actually done this myself, since I haven't had the time to get it all done, and because I want to have the wires going from the mirror into the door harness to go through the wire loom, so it's not a big homemade-wiring-job mess.
I think what I'm going to do for that is take the stock 3-hole terminal cover off of the harness end of the mirror wires, and put the three wire terminals into the 7-hole jdm terminal cover. Then leave the outer 4 (2 on each side) wires coming from the jdm terminal cover, and try and run those through the existing loom, but the space in the loom is already pretty tight, so I'm not sure how I'm going to do that exactly.
Once the wires are through the loom and under the dash, there are 4 empty holes in the blue connector (IC1) which I'll use to keep everything neat. From there, run to the relay behind the dash. This all seems to make sense in my head and on paper, but we'll see how it plays out in reality. I mean, it'll be functional, but as far as fitting everything and making it look pretty, that part's still up in the air... or on the floor of my basement as the case may be.