If you have made a toile of a princess seam bodice and you notice that the curves doesn't follow the shape of your bust, you may want to adjust the hight of the bust apex on the pattern to better fit your body. Below I will show you how to move the bust apex up or down so that the princess seam curve will fit your body better.
FIND OUT HOW MUCH YOU NEED TO RAISE OR LOWER THE BUST APEX
Mark on the toile where the bust apex is on the pattern. The bust apex is where the bust curve is the fullest. It might also be a notch on the pattern to illustrate where the bust apex is. If you didn't mark it when you cut out your pattern pieces, do this by placing the pattern piece onto the sewn toile and mark where the apex is.
Put on the toile and make a mark on the fabric where your bust apex is. Your bust apex is where your bust is the fullest.
Take off the toile and measure the distance between the pattern apex and your bust apex. Take note of 1) if you need to move the pattern apex up or down and 2) what the measurement between the pattern apex and bust apex is. We will be using this to adjust the pattern piece.
ADJUST THE BUST APEX ON THE PATTERN
Line up the center front bodice and side front bodice pattern pieces at the bust apex. Draw a box around the bust area and cut it out.
Depending on if you need to move you bust point up or down, move the box up or down with the measurement that you noted in the last step (when you measured the difference between the bust apex on the pattern and your body).
Tape the box down and place paper underneath to fill in the holes. Redraw the princess seam curve.
Cut out the pattern pieces.
Sew another toile to check the fit, or go straight to your good fabric if you feel confident about the adjustment!