I am both quite short and in possesion of a full bust. Both of these factors create fitting problems, but sometimes together they provide an opportunity for a simple solution.
This dress has a seam running under the bust, all the way around the dress.
In any case, when I put this on striaght of the (sales) rack, the front is pulled up, and the back falls down, in such a way that the bodice seam and the hemline are noticably lower than the front. But the front fits well, so I decided to run with it.
The first thing I did was to try the dress on, and pin where the back bodice seam should be. I also had a look to decide where it should taper from. I decided to bring it a bit around the front, and I pinned that spot too.
Then I unpicked the seam, making a top and a bottom piece.
Then I drew in the taper with chalk. I used a french curve, flipping it over for the other side to make a nice smooth line.
Then I trimmed this away, and put the dress back together.
I tried it on, and decided to take another 2cm out, so I repeated the process. When I was happy with that, I serged the seam.
Please forgive the hair. The weather was just a little warm. But I'm quite happy with my quick fix.