Not sure I agree with some of the statements here. You can use regulators with the power expander when using 5 cell Ni-Cd or Ni-Mh batteries if you are not comfortable with unregulated 5 cell voltages . The only issue with using regulators is that it is almost impossible to get them balanced so only one battery will be supplying current unless it fails and then the power expander would switch to drawing from the other pack. The choice is yours. Take a look at the connection diagrams on the smart fly website.

Marty