Attached is another script, with a conic le, and a 3pt te. (According to MoI docs, the conic is a portion of an ellipse.)
The apex of the conic was hard-coded, based upon MoI previous distance measure of it's z coordinate.

The attempt to join the 4 curves, non-interactively, was not successful. Join factory created duplicates of the 3 non-mirrored curves.
Seemed like the mirrored curve factory did not .calculate the Object list. (?)

Without the non-interactive join, it is just as well to let the user interactively add the conic.

I think that is about it, for this project...