Also, remember that the dart on the chest plates may make things fit differently in sintra or metal. I had a much more, umm, severe need for curves, so more darts, and then had to completely change everything when I noticed the sintra fit differently (read: badly) than the paper which had been drafted and formed to fit me. I ended up actually rotating the chest plates 180˚ and swapping the sides they were on (it was strange, really. I couldn't believe that it actually worked).
This, sadly, means that I now have to redesign and recut the ab and collar plates as retrofitting them to the new shape didn't work. My collar is going to end up similar in shape to yours. I haven't posted pictures of the current configuration on the forum yet, but this post is basically reminding you to expect the unexpected.
Unless you have a great deal of patience and money to replace things, I personally recommend fitting the chest to your desired shape first and then reshaping the surrounding templates as needed before you cut them out of your material. I also waited to cut the edge with the diamond until I was happy with the fit. This may not be how others do it (I don't know), but if it might help, great!
Note: contrary to Kris' and Garden's suggestion, mine DO cover my entire breast, but because of my shape, and the bra I've got, that was necessary to get the spacing of everything right.