I modified the official step file. Make the back completely flat.
Now it is fdm-friendly. Carefully remove one layer support under the power button, the button also works.
I also cut a hole for easy accessing the tf card of luckfox lyra.
Here’s the modified step file and 3mf project:
The filament is polyterra pla. The print finished in two hour.
It would be nice if you put this model on printables or other 3d printing sides.
Now core module can be easily swapped. No need to worry about damaging screen.
Files are uploaded to google drive.
Just an initial idea, maybe less cutout over the lcd cable to make it easier to lever out modules ?
Polyterra pla is just fantastic. Nicely done!
I thinking about adding a external usb port on the topside.
I give it today a shot in freecad.
BTW: great design. I like the threaded inserts!
One thing I’d like in a custom back case if I print one is a little storage slot for the allen key. 
Curious, how does this model prevent screen damage?
see other posts about how they get the screen damaged when swapping core module. This case just hold the front case, mother board and screen together when swapping core module. The screen won’t pop out and get misaligned.
I leave the link here also.
can you modify the back opening to the same as the one that covers the batteries ?
This looks like very good work Michael keep it up.
Ooooh I get it now. That makes a lot of sense.
Any way you could modify your first design to support a click in cover like the batteries or perhaps use regular nuts instead of heatset inserts?
