I don't think boning is going to solve the bulging issue. You just need to take a horizontal dart out of the back, so that the shape of the dress conforms to the small of your back. If you have a bodice/skirt combination, then it's a matter of removing the zip, shortening the bodice at the back, re-attaching the bodice to the skirt and re-installing the zipper, problem solved.
Feel free to PM me if it isn't clear and I can maybe sketch out a short tute for you. I get this problem all the time with most commercial patterns. It's annoying, but an easy fix.