Stackable holder for RBPi 3B+ and usual breadboard.
Special considerations for bolts:
Printed with 0.15 height resolution,
260 C nozzle temperature(PETG on picture),
20% fan speed(otherwise it melts), fan starts working only after bolt header ends(about 5.2mm) and 2-3 layers of bolt thread printed - otherwise it becomes weak point.
It depends on your plastic, but for good strength you need high nozzle temperature for better adhesion between layers.
Bolts are 6mm diameter
Nuts are 6.7mm inside diameter.
https://www.thingiverse.com/thing:193647 - bolts and nuts customized from them
https://grabcad.com/library/raspberry-pi-3-modular-case-1 - Pi case
Added PCA9685 module