yes whargoul thats pretty much it. if the value is 0 the length will be projected on the line, else it will take the vertices that are next to the most outer ones and move them with given distance on the line, the other vertices are always projected.
I added a dialog which optionally lets you use fixed distances for the outer vertices, a distance of 0 will use regular projection length for those as well (as default). EDIT: did a new version 0.8 size of edge series affects outcome for 1 edge it is turned to a loop of 3 edges, and then modified for 2 edges, simple…