Well, since you are leaving it open for a future use, I'd say split the uv's just under the breast along over to the armpit.
That'll allow you to scoot the upper part of the torso away from the stomach area so you can unfold the breast enough for as much room as you feel you need. Then for testing make a cross type pattern there so you can see that it'll carry over. I'd also pay close attention to the area directly above the breast as they tend to get pinched alot, and it makes texturing that area for straps, necklaces, lace, etc annoying.
If you are going to use this as a base model for yourself to work on, you can always adjust your uv's for each occasion that you come across.