The default segment was longer that the distance between posts (2.55 m, defined by the evenly rule), so RailClone was creating a single SLICED piece between posts, which never was instanced.
I have shortened the default segment a bit, enough to make it shorter that 2.55 m. In this way, now fits two pieces between posts: one large (a full default segment that is instanced), plus one additional tiny segment needed to complete the wall until the next post. The key is that although this second segment must be sliced, the number of polygons is significative lower than in the original scene (in fact, it is not even visible for the standard posts).
I had to modify the pivots of the objects as well (left aligned for default, and centered for the post). I have sent to you the modifed scene by e-mail.