Is there a description of how S3D determines the spacing between paths / neighboring extrusions?
There is the Advanced => Overlap profile setting, but that applies only for the junction between perimeters and infill.
Been reading a page on this from the Slic3r Manual (http://manual.slic3r.org/advanced/flow-math ... see the Spacing Paths section about half way down).
Maybe the S3D Path Spacing algorithm is proprietary? (Hmmm ... if that's the case ... it could be reverse-engineered by micro-measuring printed parts or even by some analysis - some dastardly challenging analysis - of the G-code).
Maybe I'm overthinking this, but I do think path-spacing is a key element in the interplay between other parameters such as Extrusion Width, Extrusion Multiplier, Nozzle Diameter, etc.