Hum... I don't know if this suggestion has been made yet but I experimented with something new this year at AX'03. Instead of using duct and sports tape, I used one of those sporty back brace support things ^ ^;; A friend of mine brought it from her house, it was her mother's. It worked really well for me and it wasn't as harmful to my breasts as tape usually is because the brace itself is one wide compressing strip. It toned me down from a C cup to a flattened AA or something. You can wear it with the padded side against your chest or the elastic side against your chest. It never slipped nor was it any more uncomfortable than tape ^ ^
On the subject of tape though! I found it more comfortable taking a deep breath to widen your chest cavity a bit and holding that breath while binding with duct tape or sports tape to give yourself a little freedom without sacrificing the look of a flat chest. That way you know the tape isn't so tight that you can't take a deeper breath if needed.
I love bodices and corsets, wear them to the local Ren Faire and Dickens Fair XD