Tested Print Settings

Printed successfully in PLA (not necessarily optimal — room to tweak):

• Orientation: face up (studs facing up)

• Supports: generated tree supports

• Brim: 5mm (sometimes worked without)

• Layer height: 0.2mm (0.4mm nozzle)

• Wall loops: 4

• Top/bottom shells: 4

• Infill: 80%

A quick test in TPU (~100% infill) suggests it may actually work better in flexible material — the snap fit is more forgiving and Plus-Plus connections feel more natural. See the (untested) TPU variant files.

Credits / Inspiration

Inspired by https://fffff.at/free-universal-construction-kit/ — a legendary 2012 project by F.A.T. Lab + Sy-Lab that published adapter pieces between 10 popular construction toy systems. This hybrid Duplo ↔ Plus-Plus BIG piece extends that philosophy to Plus-Plus, which wasn't in the original kit.