Everyone knows that the voltage readings on the UI/LP are way off. So here's what can be done about it:

Copy the following code into your "Voltage custom.ini file" (Motherboard Monitor 5 -> Data -> Voltage custom).

[custom]
V1=$20*0.016 // Vcore
V2=$21*0.016 // Vagp
V3=$22*0.016 // +3.3
V4=$23*0.016*1.68 // +5
V5=$24*0.016*3.8 // +12
V6=(($25*0.016)-3.6)*5.14+3.6 // -12
V7=$26*0.016 // Vdimm

Double click the "Voltage custom" file and it will open in Notepad. Copy the above code, Save, and restart MBM. The -12 will be displayed accurately.

The original code that MBM uses for our mobos looks like this:

V4=W83627HF Standard 5
V4V1=$20*0.016
V4V2=$21*0.016
V4V3=$22*0.016
V4V4=$23*0.016*1.68
V4V5=$24*0.016*3.8
V4V6=$25*0.016
V4V7=$26*0.016

As you can see, "V4V6" is the -12 and it's not coded correctly.

Anyways, to change any of the voltage readouts, the way to do it is with the "compensation multiplier" (the 0.016, 0.016*1.68, etc).
Increasing this value slightly will give higher readouts and vice versa.

For example: I have my 5V rail set to 5.2 and it's currently reading 4.95. I want it to read 5.2, so I increase the compensation multiplier in V4 from .016 to .01683. The code for my 5V line looks like this:

V4=$23*0.01683*1.68

An easy way to figure out what the comp multi should be is to use this formula:

(new voltage * comp multi) / old voltage = new comp multi

new voltage - what you think the sensor should read
comp multi - the "0.016"
old voltage - the current MBM voltage readout


so if

new voltage is 5.20
comp multi is 0.016
old voltage is 4.95

(5.20 * .016) / 4.95 = 0.01680808

I've rounded it to .01683 to get a readout of 5.20. Thanks to Alex and CCristo at LiveWire for supplying this info.