Thank you Michael.

I'll do some tests.

I guess that the "curve's parameter space" has to do with the NURBS representation?

- Brian

Using cPlane at the centerpoint, I'm intersecting the "waist" of an extruded (or lofted) pair of circles, (an oblique cylinder), with
a plane, which is a "belt" ellipse. (Like a person with a belt around the waist.)
The ellipse formed often has a different start point than the starting cylinder. I'm trying to move the start point to match the cylinder seam.
It is easy interactively, with a specific cylinder...