Can I plug batteries with different mah in my Kraton V4?

[Greengaunja]

It would seem to me that if the batteries were uneven then voltage would balance out once the were plugged in series together.

More likely one will drain below storage(damage zone) because the higher one will prevent LVC when needed. ESC reads one current voltage, not individual voltages. At least that's what HRB told me.
There is no "balancing it out". One battery has more juice than the other

 

[Sean 1978]

I realized today that they would balance out but the current would be incredible and not good for the charge of one and discharge of the other.

 

[slick2500]

I realized today that they would balance out but the current would be incredible and not good for the charge of one and discharge of the other.

Yup if the difference is enough you can have a very nice fireworks show.