I finally moved over and using the cifs_mount script, it was pretty straight forward and easy to setup. I have all the console games on the NAS and keeping the arcade core games on the SD card, it's easier to manage this way as I'm using the update_all script to get the latest arcade core releases etc I've not tried PSX yet so can't comment on loading speeds or any game play slow downs etc
MiSTer FPGA is an open source project that aims to recreate various classic computers, game consoles, and arcade machines, using modern hardware.
mister-devel.github.io