Help with wiring controls for a retropi build

[RatFink]

Hello - I am doing my first build of a control panel using a 2 player Sanwa control kit from Game Room Solutions.
This kit has the same button configuration as the one shown in this photo:
https://gameroomsolutions.com/wp-content/uploads/2016/11/GameRoomSolutions-Control-Panel-Large-1.jpg

and this is the wiring diagram that was included:
https://gameroomsolutions.com/wp-content/uploads/2018/10/GRS-HyperPie-Layout-XinMo-2-Player-with-MicroUSB-9-20.jpg

I have buttons 1-8 and joystick for both players already wired, but I have a couple more questions before proceeding.

The diagram is showing wiring for buttons 9-12 on both sides of the board.  Should I just use 1 side of the board to control these buttons or am I supposed to connect these buttons to both sides of the board?

Also:  the diagram shows wiring for buttons 13, 14, 15, mode, and VCC.  I'm not sure what to do with these connections.

I sent in a message to Ryan at GRS, but have not heard back yet and didn't want to trial and error it on my first go and possible mess something up.

Thank you very much for any info you can give.

[barrymossel]

You can map "any" button to those functions in RetroArch. https://github.com/retropie/retropie-setup/wiki/retroarch-configuration

So how you wire it doesn't really matter. Just figure out to what buttons the wiring refers and set those to the desired functions.