Apologies to the marvelous French and Saunders, and thank you both for the great image. The most obvious pivot point is the bust point. So where is it? A daft question perhaps, but everyone will have a different opinion and every woman will know that it depends on your age, current bra, or not, and many other factors that I wont go into here. Every brand will have its optimum bust point position, relative to its core customer and hopefully marked on the master block. But even then, styling will have its impact: a boned bodice will fit differently to bias cut slip dress. To accurately locate the bust point position, I ask my client, be she private or a model for a High Street Brand, to wear a well fitting bra and measure the distance from the SNP (side neck point) to the bust point. Then use half the distance between the bust points, measuring from the CF. Where the two intersect is a useful position for the bust pivot point.
But let me quote Philip H Richards, writing Dress Creation in 1937, a text book for student dress designers and cutters of the time. 'Finally I would like to warn you against too much theory. The human body is far too uncertain a quantity to reduce to mathematical formula. It is wise to remember we are trying to make patterns, not to work out sums.'
A sober warning, but when making for mass production some basic 'land marks' of the body are needed. The bust point is one, the elbow, back shoulder prominence and waist to hip darts are others. How you use them is quite another matter.