Hello folks,
I made a second Runeaudio box and added a few tweaks so that I can turn off the player with the same power switch as the one used to power on, triggering a clean shutdown instead of abruptly cutting power.
I suppose that can be of interest to some of you, so I've translated the blog post I originally wrote in French to English.
It's there :
https://www.colino.net/wordpress/en/archives/2019/01/16/diy-clean-raspberry-shutdown-for-runeaudio/
Hope it helps

Colin