A way to correlate the 30/90/120 page rule in screenplays to Dramatica is as follows:

1. Pages 1-30 = Signpost #1
2. Pages 30-60 = Signpost #2
3. Pages 60-90 = Signpost #3
4. Pages 90-120 = Signpost #4

This is a PURELY structural view and does not account for Journeys as independent "pieces." The structural view is also the "author's" view and therefore the least touchy-feely way to analyze a story.

The "audience" view of a story, the MOST touchy-feely way to experience a story, would be to look only at the journeys:

Journey #1 == begins somewhere between pages 1 - 30

and ends somewhere between pages 30 - 60

Journey #2 == begins somewhere between pages 30 - 60

and ends somewhere between pages 60 - 90

Journey #3 == begins somewhere between pages 6 - 90

and ends somewhere between pages 90 - 120

The leftovers before Journey #1 and after Journey #3 become the "prologue" or setup, and the "epilogue" or payoff/author's proof.

The Aristotelian "3 Act" structure is most akin to the 30/90/120 form with which you are familiar. It happens to be a blend of both the author AND audience perspectives and sort of fits the following format:

Pages 1-30 = Signpost #1

Pages 30-90 = An amalgam that consists mostly of Journey #2

Pages 9-120 = Signpost #4

The primary advantage of this approach is that it provides partial author and audience perspectives meaning that you can (to a limited degree) both logic the story and feel the story. The disadvantage to this approach is that it is neither fish nor fowl and therefore you cannot DO anything SPECIFIC with the story. You can only get generalized impressions about the story.

Since a finished work MUST account for both the author AND the audience perspectives, and should work for BOTH of them, there are specific guidelines you should follow. These, however, are not unbreakable RULES and, in fact, the guidelines have pretty fuzzy edges. Specifically, the guidelines I am referring to are both the Signposts and the Journeys provided in the Dramatica approach to story. Where one Signpost leaves off and a Journey begins is a matter of debate. In point of fact, each are coexistent in a story and it is only our perspective (as author or audience) that impinges these "edges" on the seamless continuum of a story.

As tools, use either Signposts or Journeys as your primary act progression reference "aid." Then use the other one to check your work and/or fill in any gaps you may find. By doing this, you are less likely to inadvertently slip into a blended view that might allow for inconsistencies or "plot holes."