A very quick look at where I've got to on this project.
I've got a common ground button PCB.
I removed the cartridge jack from the motherboard, and stuck it on some flying leads. there is an Acrylic adapter that makes it the same as the DMG version.
Screen hole has been embiggened to suit the SP's screen. I'll get a new facia printed at work, hopefully.
Still to do:
Wire buttons. Should be easy, need to work out where the shoulder buttons are going.
Wire and mount Switch, Volume and Link port. And Headphone jack and Speaker.
Work out charging. And Batteries.
Work out how to fit both DMG and Advance cartridges.
Work out how the case will fix together - some screw holes were removed to fit the screen.