Probably still not as thorough as you'd like, but this is all the time I feel like investing in it.
My shifter is mounted in a CP and isn't wired the way you need it anyway.
I found some pics of it on BYOAC though and drew the wiring on it.
I didn't label the gears because it's a PITA to figure them out with the pivoting action of the shifter reversing everything.
Easier just to wire it up and then figure out which wire goes to which gear using a multimeter to see which one is going to ground.
Looking at switches online, it seems the C (common) tab is always on the end where the lever goes into the switch body.
Adding the extra switch on the front makes it so no switches have a path to ground (no gears register) when the joystick is centered.
If the NO and NC tabs on the original switch are used instead, one gear will always be registering which could cause problems when mapping emulators or navigating PC games.