The MSI TF Gaming 280x cards CANNOT be modifed at this point in time (very limited voltage modding allowed as described below).
Although it would appear that using VBE7 and atiflash looks like it changes the voltage (shows in GPU-Z and in cgminer as new lower voltage), If measured on the card you will find no change.
This is true for card versions 3SB and above (2SB cards can be modified in this way).
The only voltage that does work is 0.943 V (Dont ask me why?).
The only drawback with this voltage is that you wont be able to hash anywhere near 700K you might get 650K at best.
So until MSI release an editable BIOS (if ever) or another tool is created that can edit it we are stuffed!
I have 3 X 3SB cards and 1 X 2SB card.
You may want to update the OP to reflect that these cards are not unlocked.