Hi jik, those are some great railroad models!

> I also played with parameters at .stl export, and found better to use more polygons and
> let the printing software to "antialias" the surfaces.

Yeah also using the "Divide larger than" parameter can be good for getting more evenly sized pieces. If you put in a distance in "Divide larger than", any polygon that's bigger than that size will get diced up further. It can help to avoid making triangles that span a large distance across the model. Something like around 1/20 of the overall size of the model can be good to put in for "Divide larger than".

- Michael