Loomis heads use 2 cuts/shaves to the sphere. These will look elipse if the face is not in profile. The shape of this elipse, centre, major and minor axis has a lot to do with the perspective if a circle on a box rotating in the space. Imagine the choped off sphere as a very round tyre of a vehicle, determine the perpendicular minor axis of the chopped elipse. Imagine the elipse on a square plane, the diagonals intersecting point will be the real centre of the circle, which will be little away from the centre of the elipse.This all will help you determine the orientation of the chopped of sphere, placement of various facial features.