Isn't your power supply adjustable? If so then you can just dial the voltage up to the correct 5.1 volts.
Some boards eat more juice than others and will require you to adjust the PSU anyway. I have one board that eats so much juice that my Candy cab can't even get the board up past 4.6 volts (but the new power supply in my Multi-Williams can be dialed up high enough to run it). I can't remember the name of the game at the moment, but it is an old Konami pinout game where you play a round tank, joystick, rotate right, rotate left, and fire
EDIT- Just remembered the name. Strategy-X