Attached is an unofficial Catenary curve creation script.

It works well in the TOP view.
Catenary2PtXY is a script which produces a catenary in the xy plane, from two points picked by the user.
Gravity is in the negative y direction.
In the event that the z coordinates of the two points are not equal, an alert requiring equal z coordinates is given.

This script uses the Opalg math, and most of the elbarto code.

Nearly all of the MoI Distance script is used to select the two points, and measure the distance between the two points.
The user inputs the chain length, which must be greater than the distance between the two points, or a catenary will not form.
In the event that a catenary does not form, even though the chain length is greater than the distance between the two points,
OR if the catenary is upside down, the Newton-Raphson method has failed, and the user can adjust the GuessRadius parameter,
to be smaller or greater than 1.0.

For a chain length that is long in relation to the x-axis distance between, try a fractional GuessRadius.
For a chain length that is slightly longer than the x-axis distance, try a GuessRadius greater than 1.

An ARCH seems to be formed if a negative GuessRadius is used.

An explanatory PDF titled "Catenary Suspension from Two Points" is being edited, and may be posted later, if anyone is
interested.

Edit: 3/23/2012 Replaced Catenary2PtXY with slightly modified htm. Now works with MoIversion 2 (Windows)
Do not have a Mac...

Still working on a version which will also accept different z coordinate values, by using a coordinate frame...