7.4v LiPo for receiver pack

[BrianG]

Depending on the UBEC quality and how a particular rx rejects noise, there might be switching noise on the power line that could cause issues. Sometimes, simply adding a 10v 1,000uF capacitor on the UBEC output (or an unused Rx slot) can help this.

At 7.4v, there is not much benefit to a UBEC over a linear regulator. A UBEC is around 75-80% depending on design and load. If using a 3A load (worst case) and putting out 6v, minimum linear regulator efficiency will be around 76%. Not much gain there. And if you draw less than 3A, the linear regulator efficiency will be higher, while the UBEC is pretty much always at 75-80%. A linear reg loses out once the input voltage gets higher, but at 7.4v, it's a wash.

You can build a linear regulator circuit (LM317T with a pass transistor and a few support components) capable of 3A or more with just a few parts available at RadioShack. Total cost could be as low as ~$10. And if you tweak the output to be closer to 6.5v, you can get it to be more efficient at closer to 85% efficient. Total size would be about that of the Koolflight BEC.