|I have learned the hard way that with soe fabrics, boning or cording will "shrink" the width of a piece. A few fabrics are forgiving with this ... but not the one I am working on right now.
Before cutting out everything, cut a section of a specific length of both layers to be boned/corded as wide as your finished section and about 4 inches tall (or six if lighter weight fabric) then sew the number of channels you plan to use. insert bones or cords, then measure to see just how much it shrinks.
*ETA* Set up the test strip as the shorter and most corded/boned section of the finished piece. This takes prior planning, but is much quicker than doing *3* versions before it's right ... ask how I know this.
Example: I am working on the corset in Simplicity 2621 with a front opening, so I have 3 pieces per half. The cording shrunk the pattern 1-1/8 inch at the bottom and 1 inch at the top, so I added half an inch to the front section, half an inch in the middle of the side section, and 1/4 inch to the bottom of the back section (topline on back piece is the same). All 3 pieces have one edge on the grainline, so the extra fabric needed to be distributed evenly among the sections.