Work on overall pec size, and chances are it will all fall into place. I used to have HORRIBLE pecs, but once I stopped caring about different angles, exercises, and blasting this and that, etc (luckily for me, I learned this very early on), my pecs took off. My main movment was weighted dips, and they did me wonders.
Try a low incline bench press or reg. flat bench and weighted dips. Just do those two exercises. Work on building up your strength in those two movements. Eat good, and don't neglect other body parts. You will most likely fill out not only your 'lower center pec' but everywhere as well. Good luck.