Hmm.  Very strange. 

All I changed for the pose was the keyframing for the trans and rot dials for the right thigh, right shin, and right foot.  Possibly the translation keyframing could create some issues, but it looked like there were already keys for each frame for the trans dials of all actors in the pose.

If the stride length of the right leg was increased by mirroring from the left side, that would explain the discrepancy in the number of frames, perhaps.  I'm more toubled by the leg flying out behind.

Something I didn't do was adjust the hip rotation in the altered frames.  Possibly that should mirror the hip rotation in the frames from which we've borrowed?

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Cage can be an opinionated jerk who posts without thinking.  He apologizes for this.  He's honestly not trying to be a turkeyhead.

Cage had some freebies, compatible with Poser 11 and below.  His Python scripts were saved at archive.org, along with the rest of the Morphography site, where they were hosted.