I own a few arcade cabinets and with the exception of my "dedicated" Sega Naomi and SNK Candy Cabinet, I never mount boards inside my machines. You are suppose to screw the arcade PCB into the side of the arcade cabinet, if it's an North American cabinet, or onto a wood board and slide into a very compact Japanese cabinet.
As a collector, I rotate through my arcade games frequently, and having to mount the PCBs everytime I want to play a game got tiring very fast. So here's a simple fix. By attaching a universal PCB holder to a piece of wood I can keep my PCBs secured from shorting out on the metal interior of some of my cabinets while also making them easy to move around if I'm playing the PCB on my Supergun rig.
I wanted mine to look nice so I just purchased a bamboo cutting board from Amazon. I know this isn't groundbreaking but I'm always shocked to see fellow enthusiast running arcade PCBs all haphazardly. Just screw the PCB Holder onto the cutting board and add rubber feet to the other side to keep the cutting board from sliding around and just like that, you made yourself a versatile tool that will help protect your arcade boards and also make playing them a lot easier.