Missed this threads rollout because the Forum is still running squirrely, and things still seem to appear only willy nilly like. If you don't happen by when a when a recent post appears out of place, typically in the general forum questions section, you may not see it at all.

Historical structural ridges - done a lot of looking at a lot of frames in alot of locales, and I've not seen one ever, and I don't expect to.

Here in Common Purlin Land, one finds a four sided Ridge Purlin, (Rectilinear not square - With one of the two shorter sides clipped at roof plane) in frames on either side of the transition from Scribe to Square. This serves as nailbase, and like the other Common Purlins, to carry the thrust and dead/live loads of small subsections of the roof deck laterally to the Principal Rafters