Now we move to the front half of the block. At the waist height, measure forward of the centerline to the ¼ waist measurement.
At the bust height, measure forward of the centerline by the ¼ underbust measurement. Extend that line by the bust modifier. Make a mark.
Draw a slanted line between and extending beyond the two new marks. This is the front side.
Create a curved waistline as on the back quarter, squaring to the front side.
Verify the length of the curve is the same as the ¼ waist measurement. Move the mark and re-draw the front side if needed. Steeper curves are more likely to need modification.
Along the front side, measure the distance from the waistline to the bust height. Make a mark.
Create a curved bustline from the new front side bustline mark to the center line. Verify the length is the ¼ underbust measure plus the bust modifier. Adjust the mark and front side if needed.
Find the intersection of the straight bust height line and the front side. Square the ruler to the front side at that intersection, and draw a line back from the front side.
Find half the total distance from the bust to the natural waist (in this case, ½ of 7.25, or 3.625, which rounds to 3.5). Extend the front side below the waist by this amount. Depending upon the individual, and the length of the torso below the natural waist, this extension can be significantly longer without discomfort or inconvenience. However, I have found that this amount of extension is comfortable on a majority of people. Alternatively, take a direct measurement of the front of the torso from the underbust to the lowest comfortable front centerpoint of the stays. Use that measurement instead of a mathematical approximation.