Quote - Cage, is this the kind of pose you had in mind?

That's basically it, but the pose I was testing was more extreme (a pose by Davo from that other site with "Render" in the name, if you follow...).

In the first render you've posted of the pose, there seems to be just a bit of the squinching, at the very top & back of the shoulder.  (Visible here on the figure's right, but presumably present on both sides.)  The upper tricep region is just starting to collapse at the edge of its bend zone in that pose, and will get worse if the pose is taken any further.

Given that the problem is worst in extreme poses, it's certainly not a joint parameter crisis.  If one can envision such a crisis.  :lol:  But it is a greater tendency with collar Twist than with shoulder Swing, so the desirable handling for those two parameters is apparently more complex than has been determined in this thread in the past. 

I'd say the pose you've posted here is good for any natural pose, free from contortion, that a figure might be expected to handle.  I can put my own arms in slightly more extreme positions behind my back, but they're not very comfortable and are presumably fairly unnatural positions.

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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.