In order to define a plane containing a circle, I need the center of the circle and the normal of the plane. Getting the center is simple using hm_getbestcirclecenter. I have not been able to find a means of getting the normal. If it were possible to get the coordinates of two points on the circle, I could use those with the coordinates of the circle center to calculate the normal. However, I haven't been able to find a means of getting those two points.