duplo plane bits

Warning 3d printed parts may break and be a choking hazard for young children. Many glues are also toxic, you take responsibility for what you print….
PETG preferred material
“hot melt” glue used throughout
Duplo is annoying to print as an exact friction fit is required. Experiment with a small part ie (S1 or P3) and check for fit.
If too loose you can try: over extruding a little, if the holes are too loose (they are generally on the bottom of the part as printed) so squashing the bottom layers a bit can help (ie have a 0.1mm gap but have slicer set for 0.3), again for the holes you can try printing with supports / brim or raft and not cleaning these up completely afterwards.
If too tight you can try mechanical means to remove excess (sanding, drilling, reaming, cutting a few prongs off) you could try underextruding a little.
For more unexpected results you could try resizing the part a tiny bit or changing the accuracy on your slicer.
Anyway probably worth making sure your