Butterick 5814. One thing that's very important in a design like this is to stabilize the neckline. V-necklines are notorious for gaping. That's because the fabric is usually cut directly along the bias--the stretchiest part of the fabric. If it's not stabilized, the v-neck will continue to stretch over time. (Note: sometimes a design will have you cut the bodice piece so the v-neck is placed along the straight grain of the fabric, but it's more common that you'll see the straight grain at center front, which places the v-neck on the bias.)
You'll want to stabilize your neckline as soon as possible after cutting.
First, mark the neckline seamline with chalk (in other words, mark 5/8" in from the cut edge of the fabric). Here, I'm working on the right front bodice piece.
I did the same thing on the top of my raglan sleeves.
Now you have a neckline that won't stretch or gape!
P.S. I'll be taking the rest of the week off blogging in honor of Thanksgiving. I hope you all have a great holiday and weekend!