Alright, I didn't want to post again until I was done but it is taking me a while. I finally got all 4 controllers hacked. I had 7 different controllers to work with and found out that only 3 of them had common ground. Of those 3 one was an original fatty xbox controller with little tiny traces and tons of some kind of mask applied to the board so that when I tried to solder I couldn't, instead of copper contacts it had some kind of weird graphite or something that was solderable either. Well, after ruining that controller I slept on it and realized that the smaller 3rd party controllers didn't have common ground but the ground was just spit over 2 circuits, 1 for the D-Pad, select, and start, and then another ground for all the other buttons. Anyway, I don't know why I'm telling except to document my story.
I got my constant current driver in the mail from Hong Kong and wired it up and it works great. Just need to build the relay circuit and then hook that all up through my xbox power supply.
Here's a couple of pictures including my not so pretty wiring job. I have a hard time spending too much time on any part that I know isn't going to be seen by anyone but me. I decided to go with black tmolding instead of the green. Didn't match very well. Sorry about the blurry ipad pictures, the next post I will show the whole thing all done with an HD video.