Got everything assembled and working.
The panel shipped (with UPS expedited) in 2 days (!) from Hong Kong, which I was pretty impressed about. I need to do some more cable management, and some tidying up around the shim, as my cutting to size wasn’t perfect, but otherwise it’s all worked out pretty well.
This is the 5V - 12V step-up converter. Powered from the RAVPower charger and supplying 12V to the panel. So far it hasn’t even got warm to touch - I’m going to leave it running but it should be well within its limits:
DROK converter to display panel:
The second USB output I’m using to drive the Pi, via a PowerBlock. (Yes, I know I should have used standoffs rather than blutack - I didn’t have any spare - and yes, I know it’s shitty soldering :) :
The power switch is latching on/off with built in LED:
I now have a working Picade with a single power cable leading into the chassis. The power switch does NOT control the screen; however, when the Pi is powered down it goes into standby which is close enough for my purposes.
Still need to upgrade the buttons and add some funky lighting.