I have recently began testing small prints with 3d Solex 0.25mm nozzle on UM3 extended.
The best settings using PLA are as follows:
0.6mm layer height (have also tried 0.1mm)
0.2mm line width (previously testing 0.22mm)
0.5mm wall thickness
Z hop off
Full retracts, Latest version of Cura default settings (have tried 6.5mm)
Temp 180 (have tried going as low as 175-190)
Speed test have ranged from 15-30mm/s. I have done this by changing just the print speed setting and letting Cura adjust the others, and have also tried locking all movement speeds to the same number.
Bowden tube is a