Are you making the JCM from scratch, or working from the versions ported over using Morphing Clothes, as you mentioned earlier?  The JCM's for the thigh joints should be set to hit 1.0 when the thigh bends -60 degrees.  The same value is true for the thigh spread, but right is negative and left is positive.  So the sixty degree bend is the critical point.  Then you can just copy over the ERC for the JCM's from Antonia.

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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.