I would like to mount my extra TBS 59 camera to the Discovery Pro Gimbal and use the video switch feature. How exactly should I wire it so it is recognized as video/channel 2 (what specific pads or wires should I solder to?) - I tried using the provided 3 pin connector from the gimbal IMU, but that did not output a picture - after hitting the cam switch all I could see was the IOSD data.

Building the Discovery pro has been an awesome experience, and not too painful thanks to this community .
The only modification I have made is added IOSD mini (I simply cut the VTx video cable and soldered the IOSD video in/out in line). Since the TBS 59 camera isn't compatible with IOSD, I swapped it for a PZ0420 600TVL camera (cut the CAM 12v cable and soldered video/power/ground in line so I could use the same CAM plug). All works very well!