Some more fun with diagnostics...
Indiana Jones and the Temple of Doom, as we know it, is 114 minutes long. Considering that there's credits involved in that, it's about 108 minutes of film footage. (I don't understand why the earlier figure I'd found cited 118 minutes.)
Part I would end at about 27 minutes, with Indy and Shorty's conversation about Sankara and fortune and glory.
Part II would end at about 57 minutes, with Indy, Shorty, and Willie having just escaped the spike room.
Part III would end at 84 minutes, with "Right. All of us."
Part IV would end at 108 minutes, with Indy and Willie embracing.
Part I would have 27 minutes, Part II would have 30, Part III would have 27, and Part IV would have 24 minutes (and, perversely, about 7 different action beats.)
You might be able to push Part II back a little to be during the spike scene, or
forward a little to get to the first site of the altar to Kali. They're all choices that make some sense, but I'm finding myself favoring a methodology that doesn't slice action sequences into bits. If others were coming forward with their sketches of how it might work (I kid, Stoo, I kid!), we could have something to talk about. Incidentally, while it's entirely apart from what gabbagabbahey initially suggested, I suspect that a more action-oriented approach might be one that sliced the films into segments closer to being 20 minutes in length rather than 30. That's also the length at which Temple's single best "where do we go from here?" moment gets to be a segment end, which is to say, the close-up on Indy's newly evil face at 74 minutes.
* * *
Last Crusade is 125 minutes long. Adjusting for 6 minutes of credits, that's 119 minutes of material. As such, the segments should each be almost exactly half an hour long.
Oddly, it also seems to be the film where a straightforward cliffhanger approach seems most natural, dictated both by placement and by the one literal cliffhanger moment where Indy's death seems a certainty. That's at 95 minutes, meaning the final segment of the film will be shorter, and the ones prior have a little more leeway to play around in.
So:
Part I could end at 35 minutes and the dropping of the match as the rats begin to run down the catacombs. That makes this the longest segment, which isn't bad, since it is broken into 3 discrete segments, plus the smaller Coronado scene.
Part II could end at 66 minutes with the pan up to Berlin on the road sign. It's less actiony, but if you hold for the first glimpses of the burning books, it would have potential.
Part III, as before, could end at 95 minutes, as Indy sees the edge of the cliff.
Part IV ends at 119 minutes, as they ride off into the sunset.
Part I is 35 minutes long, Part II is 31 minutes, Part III is 29, and Part IV is 24.
* * *
Then, Kingdom of the Crystal Skull is 120 minutes long, with 5 of those being credits, leaving us with 115 minutes to divide up.
Doomtown is rather prior to the point of being a possible cliffhanger in a four-segment structure. This suggests that an attractive approach to the divisions in this particular film is one that tries to find the moodier, more foreboding moments and puts a division there.
Part I ends at 27 minutes, as Indy boards the train that will presumably take him to his new life.
Part II ends at 56 minutes, with Indy and Mutt at gunpoint upon emerging from the cemetery.
Part III ends at 90 minutes, with Indy's "Because it told me to." (As an aside, the exchange that happens after the waterfalls is much better than the preceding material would suggest.)
Part IV ends at 115 minutes, with the wedding guests, followed by a hat-less Mutt, leaving the chapel.
Part I is 27 minutes long, Part II is 29, Part III is 34, and Part IV is 25.
* * *
Now, I'm not a serials guy. I'm not versed in them, and I've barely seen any of them. This means that I don't have a great sense of where exactly the divisions are usually placed. Are they when danger begins? Are they at the tensest point in the action? Are they at the point right where the way out is revealed? Or just before that point?
The other question: is the placement of segment divisions in the old serial manner one that would really shift properly into this new idea in this new age. While action based cliffhangers could be a little hard to make work in a more modern era, particularly with regards to the reveal of the precise solutions that would come into play, I fear that some of my moodier transitions feel more akin to where episode breaks come in the long-form television dramas of today.