QantumForce bioseditor seems not to recognize the 256 bit bios. (I tried)
Rabit does not support the 2900 bioses (as yet).

FF01 seems to be a 'proxy' - pointing somewhere els in the bios-file to the 3d voltage. FF01 is safe to overwrite with the HEX value corresponding to the desired voltage.
How to do this is described earlier in this thread. (remeber to invert the hex numbers!)