I went to an American Sewing Guild meeting a few weeks ago where a few women presented the bras they had made at bra making workshops. They're hoping to get one going down here, which has me really excited. The lady who they want to have come, Ann St. Clair??, will help you make a custom fitted bra and will advise on fitting issues after the workshop also.

One of the things the ladies mentioned was that you can increase cup sizes if you have been wearing poorly fitting bras and then start wearing ones that fit better. If the fabric and the side is properly fit, it will move breast tissue that has shifted to your side back to the breast. They also mentioned that you should replace bras every 6 months. If you're making your own, that's a lot easier to do. I know I'm bad about hanging on to mine way too long since it's hard to find ones that come close to fitting.