haven't been paying as much attention to this site since the weather went downhill around here.
As stated above, you definitely want a relay. These things pull a bunch of amperage, you'll definitely keep blowing fuses if you try to run in parallel with any other item on the bike. There is plenty of room to store a relay under the seat (in the battery area). You really only need an automotive SPST (single pole single throw) relay that lacks the extra terminal that is closed when the switch is not active. The image posted above is from a SPDT (single pole double throw) relay. Personally I try to use the right tool for the job. If you chose to use a SPDT, make sure you either clip off, or adequately cover the unused terminal or you could find that you're shorting things out, causing fires, etc.
Personally, I'd stay away from using the brake light as your switched wire. The last thing you need is something to short while you're riding and lose your tail light. Pick something else. Personally, I picked the license plate light.
Think about the routing of the wires. You'll want wire covers if you want it to look professional as they will be visible in some locations, and wire covers prevent the wire insulation from becoming worn and shorting out on metal parts.
Mounting of the switches seemed to be the biggest battle for me. I don't like the cheesy looking switches that come with the kit. I got one of these:
http://www.motorcycle-superstore.com...WT.MC_ID=10010
That switch fit perfectly on the left handle bar (of a stock ninjette) and provides a clean install. Nothing looks "tacked on", like it would with those simple toggle switches. Plus, it provided an additional momentary switch (advertised as a kill switch), that I wired up to a garage door opener... now I can pull straight into my garage when I get home without fumbling in my jacket pocket.