Using an Arduino Nano board which is mounted using: https://www.thingiverse.com/thing:1586850
The 9v battery is held in using: https://www.thingiverse.com/thing:2605589
The red wires hanging out of the side are for a selector switch for game time, im waiting for the switches from ebay at present.
Smart idea and also similar to what i was planning on adding to my design, but the only reason I didn't use an arduino Nano is that I didn't have one at the time and i had all the other parts i needed. The holder for the 9v was pretty much what I was planning to add, but you beat me to it. Nice job
The 9v holder broke after one battery swap, so I wouldn't intergrate that one into your design.
The Nano holder is very tight so the board isn't going anywhere
The holder is an easy fix just print the 9v holder 105% scale or 1.05 scale depending on your software