Diagram for USB Sega Pad

I’m planning to gut a Play Sega pad for its PCB board. Anyone have a diagram (of a Play Sega of “SLS” board)? All I really need to know is where the ground signal would be. Looking at the original Saturn pad diagram, would it just need to be scratched somewhere in the middle of the board?

A Multi-meter if your best friend when it comes to finding a common ground.
Honestly even if the Knock off USB SEGA PAD is cheap, for a stick project you are better off coughing up the dough for a better PCB with better documentation.
There are several versions of the USB SEGA PAD floating out there in the market, each with it own Quirks.

Most USB Saturn pads are very simple common-ground PCBs.

You can probably guess which is ground by just looking at it.