well so far I can tell you, theres little to no chance of editing a Asus BIOS.
I haven't found any way to open a Intel, or A64 bios from Asus yet.
Modbin won't do the job, cause they are not Bin files.

plus, you can't just change the voltages to whatever you want.
if the option isn't there in bios to unhide...
I don't think you can do anything about it to add it.
chances are, 2.8 volts is gonna be your max, no matter what.

anyways, use modbin 1.0038 and that will get you started.