Inspired by https://www.thingiverse.com/thing:2169943 

The key differences:

• the latches shape is more fdm-friendly (less sharp angles, extra tolerances)
• added springy element for better latching between elements
• added springy ends with pins for holding the boards
• step increased to 12mm, so boards with soldered GPIO headers can fit
• ~30% less filament used

The model assumes xy tolerance of 0.1 mm (empirical value from my MINI experience).

Tested with ColorFabb PLA-PHA and PLA Economy, standard nozzle, 0.2mm quality profile. Please test on 2 pieces first before mass-printing in other material and let me know if the stiffness needs to be adjusted.