Here is an alternative to other alternative case mods for the back right panel using keystone fittings that I designed and posted to thingverse. This also uses the more affordable arduino leonardo which I picked up for $12 on ebay to control the keyboard. Will create a back left panel with the same keystone fittings.
Amiga 500 Keystone Back Right Panel. Arduino Leonardo mount bracket
The Arduino Leonardo is very simple to program and much cheaper ($12) than the tynemouth solution ($65).
I will be posting pictures and steps in the next few days.