This tutorial should prove useful if you want to disable certain buttons on your Mad Catz Fightstick. It will allow you to use the On (unlock)/Off (lock) switch that is featured on all Tournament Edition, Standard Edition, and Fightstick Pro arcade sticks, regardless of the console.
Here's how it works:
I solder a separate wire to the back of the PCB (in the picture, it where the black wire is soldered). It is a designated common ground for the lock switch. This is where the ground of the button you want to allow the On/Off feature to be used is to be soldered.
So for my example, I would have one wire going to the Start signal (like normal), then the ground wire for the Start button goes to this one. The button(s) attached to this special common ground will be unusable when the switch is in the Off/Lock position, but usable when in the On/Unlock position.
Here is a video explaining the mod:
-Edward "RoyalFlush" Valdez