It might be better to do pattern grading which means you’re taking your existing pattern and going up a size or down a size, depending on what you need. Unfortunately, we don’t have a tutorial on this (yet) but here’s a link to a pretty good article on it. http://www.threadsmagazine.com/item/4368/making-sense-of-pattern-grading/page/all I hope it helps 🙂

You’re essentially doing a method known as slash and spread method at major points of the pattern in order to get an even increase (or decrease). Here’s another article from Burda which might be even more helpful as they break down a bodice. We hope to have our own tutorial on it someday. http://www.burdastyle.com/techniques/grade-a-bodice-pattern-to-a-larger-size