A lot of people have tried. I've tried upping the voltage by bios editing before, but if the card doesn't have software voltage control already it generally does nothing. Numbers in the bios can change but when measured before & after it didn't actually change anything.
I started using the soldering iron & hardmodding cards because that was what worked, with software voltage being common for cards now I work with that as much as possible on new cards to keep warranty.
For a pencil mod, try testing for continuity from the hardmod point & see if you can find a resistor that has continuity, use the multimeter to check stock voltage & try shading the resistor. then check with the mm to see if there is any difference.