IT was a massive pain in the ass, the research took hours while I looked for the best solder points for every button. After that there was all the scratching to remove the green, then the pre-soldering, the soldering, and throughout it all I had to concentrate on making sure I could still close the damned thing later. =D
But it worked, first try.
Now though I'm not so sure the Competition Pro is the right choice, but that's fine. With a neo connector on there I can use pretty much any of my existing sticks.
Now, the pics!
Here's where i had planned to drill the hole. It was a MUCH better option than the face, above the BACK button, like I suggested in the first post. I didn't have a drill or bits, so I just melted my way through with a soldering iron. I think this was actually the better plan.
You can see here the hole is pretty much complete. This is the only place on the 360 to put the hole, and it's pretty much perfect. It doesn't interfere with the battery, and you can't even tell it's there during play. It's possible that it'll block the play-n-charge unit, but since I don't have one (and batteries are cheap) I don't care too much.
This PCB is really a tiny bit of work. The traces and all connections are soooo tiny. And the chip? No f**king way I was going to try soldering to that thing, the pins were way too small to even imagine success.
Here I've labelled the vias for each connection on the other side. Since you can't solder to the switch/pad itself (which would ruin the pad if it DID work since the rubber bits wouldn't fit anymore...) I figured this was the best place.
And these are the last of the buttons. Since these ones all came up through the PCB underneath the chip, there's no way to solder to all the connections on the same side of the PCB. This complicated things a little.
Here you can see I've scratched away the green, and applied fresh solder to the vias. It's a bit of secret shame here that I seem to have broken a trace: the pad's A button doesn't work anymore (but the wire connected to the A point above works fine!)
And here I've pre-soldered the points on the other side. You have to pre-solder them, or you'll go insane trying to solder the wires to these points later.
The wires... Group 'em tight and glue 'em down!
Routing them next to the analogue stick is really the only option. All other paths will take it across some area you want to keep clear: screw holes, connectors, d-pad switch pads... This did cause some trouble with the plastic support surrounding the stick, but it was nothing the sidecutters couldn't cure!
I attached a zap-strap to the cable to keep it from pulling out of the pad and ruining my delicate handiwork...
A dab of hot-glue keeps the wires from pulling off the PCB. There's another on the top to keep the brown wire from drifting into the screw hole...
Some pointers if you want to try this:
1. One shoulder button is easy to reach (grey wire, last image) but the other is underneath the plastic trigger assembly. That's why the brown wire goes over the top of the PCB.
2. Soldering to the vias is a PITA. I wouldn't suggest it if there were any other way. Practice on something you don't like first.