I have a part that uses an ellipsoidal surface as the primary datum (-A-), a center plane as the secondary datum (-B-), and a curved surface as the tertiary datum (-C-).  I am having trouble figuring out how to properly align this part on the CMM.  FYI: The ellipse and curves are large (i.e. 100" or larger) so the curvature is slight on the actual part.

Has anyone had this type of alignment come up, and how did you align to it?  Any help would be greatly appreciated.

My apologies for the horrible drawing.  We do ITAR work and I cannot provide drawings for reference.