According to the LED Lighting Xbox 360 controller turorial, you must be able to solder the wires to somewhere, at least, you can't read it there but the last pic shows you that you must twist the wires together.
Another thing, please post/suggest what the best way it is to solder the LED-lights (single/series/parallel)
On this page
http://www.llamma.com/xbox360/mods/xbox%20360%20Controller%20LED%20Mod.htm#lighting%20the%20abxy%20buttons, I miss a few pics of where to solder those wires and how to avoid hitting any contact points. Could the Llamma team please post the (2) missing pics on completing the soldering for your X360 controller buttons?
I was reading the tutorial a few times before I found this out. Lucky for me I didn't start the project yet, since I don't have the required items (yet).
btw, nicely done

I am gonna enjoy this for sure!