I'm not usually on S&B threads, but having lost a considerable amount of weight, my back size has dropped from 36" to 27" (and may drop further). I hope the wisdom of MN can point me in the direction of a bra shop or supplier who sells 26GG (or thereabouts) as my poor neglected norks are heading inexorably southwards in my current 30Gs.
I found corsets that do the trick, but these are not exactly a suitable everyday option.