Resolution and infill by piece:
Pulley, the most critical: 0.1mm, 100% infill
Bolt and plate: 0.2mm, >= 20% infill
Arms: 0.3mm, >= 20% infill
The left and right arms are designed very tight, and some sanding is needed. Carefully sand and insert them into the panel until it fit, without struggling the front panel. It is essential that they not bend when tightening the belt, maintaining the belt-motor-pulley geometry.
Bolt and plate
The bolt needs some effort to fit into the plate the first time. Mine, at 0.2mm, fits nicely after the first time, neither too tight nor loose.