Was very tired after coming back from work today but this project gave me some more energy. I didn’t had a 12 pin right angle female header so I used two stackable 8 pin ones cut to size to make one.
I cut the end of one of the key pegs and melted a pin from a male header into it and then soldered it to secure the key peg.
I did a mockup of the flash cart and original USB cable inserted at the same time (required for flashing from PC side) There’s not much spacing but with a proper PCB or different wiring a thin flash cart case should be possible.
I’ll save the expansion connector wiring for tomorrow when I’m less tired