But aren't the S_D rules for 1/3 of a CHAPTER, not an entire graphic novel or trade paperback? A single magazine-format comic issue seems more equivalent to a chapter of a book, or a short story.

.....Aaaaannd I just realized that a third of a chapter applied to every chapter equals a third of the completed work. But again, I don't see people posting 60 pages of a 120 page manga here. It's really hard to compare a serialized medium vs. non-serialized.