@petrockblog I think you can best answer on this ;)
I saw your switch built in a NESPi case - it should fit perfectly in.
But what will happen in the following scenarios:
I use a momentary switch and press the button to powerdown (I think it's clear what will happen)
I use a momentary switch, do a shutdown via
software (Quit >> Shutdown system)
The Mausberry switch fails in this case, because it will miss the physical button press and therefore needs a GPIO signal sended to the Mausberry circuit (Take a look here).
If you don't do this modification the Raspberry will shutdown as usual but the Mausberry switch is still active and does not respond to any button switch. So you have to cut main power or reset the circuit to make it work again.