Here's an update.

• Now setting origin, endpoint, and orientation of new loop to match those of plane, as requested by Les.  This enables correct scaling of the loop.
• Fixed bug which was creating squashed/deformed loops when plane is scaled on X,Y, or Z.
• Added option to create a "Fatness" morph on the new loop, as is present on the Poser torus primitive.
• Made a slight change to the test when locating intersection candidates.  Hopefully this will improve the selections somewhat.
• Changed default setting for smoothing option to 0.0 on parameter dials.

Now I'll see if I can work out some way to handle the requested mirroring.

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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.