Digitech Jamman stereo Ext pedal info?

[legion@helpwantedproductions.com]

I'm picking up a digitech jamman stereo and want to DIY a foot switch to go in the Ext in to handle reverse only (don't need the other functions or the bulky "official" FS3X. I laos have about a half dozen various generic foot switches with 1/4" ends.  It looks like the Ext in on the jamman wants a stereo tip/ring/sleeve cable. Does anyone have the pin out or info on what goes where on the FS3X or what wires I need to attach to to just get the reverse out?

Related has anyone successfully just used a generic one button footswitch to do reverse and if so what kind of cable/connector did it have?

Sorry if this has been discussed before, feel free to point me to sites or email direct if so. Thanks for any/all help!