Only 12.5mm from the bottom of the keyboard to switch plate. To put it into perspective:
- Whitefox: 12mm
- TEX aluminum case + Sentraq S60X plate: about 12.5mm
- Planck: 13mm
I can squeeze about 1mm of height if I use thinner aluminum for middle and bottom plates. But getting plates in two different thickness for small scale projects is not economical, at least from my perspective. Using thinner plates could mean some countersinking will need to extend to the acrylic parts.
It is probably possible to squeeze 0.5mm from the upper chamber if I can find acrylic sheets in 4.5mm thickness. If going that route, then it will be necessary to replace the 5mm M2 hex spacers with 4mm ones.
If a thinner battery is available, then it should be possible to reduce bottom chamber to match the thickness of the battery.
If thinness is paramount, then it is possible to forego battery and piezo buzzer; remove bottom chamber and make the middle plate the bottom plate. I can get 8mm bottom to switch plate thickness. And this is still not including the optimizations above. It may be necessary to remove the protruding JST-PH battery connector from the Adafruit controller, but if rubber feet are being used and they are in adequate height, then it might not be required.
The faceplate is 3mm in height, but it doesn't add to overall height (it sits on the switch plate). So, it is not critical to optimize thickness here, but thinner acrylic mirrors are available, though choices of colors are far more limited.