Antonia's critical point regarding automatic grouping was the strake between the breasts, where garments that do not have a recess between the breasts and spans from bust point to bust point. The garment then is at some distance from the chest facets while the normals of the facets of the breasts point across it. I recall some cases where the fitting room generated grouping did not have a line of chest facets separating the facets of the left and right collars.

One way around this is a spandax morphed donor figure.