Aerowoof:

I wasn't trying to set you up, I thought you might have had new information! Here's some receiver information directly from Futaba:

Voltage out is based on Voltage in. Receivers typically operate on a
4.8V DC input voltage. This can be increased to 6.0V, where more
power and speed can be derived from attached servos, but a decrease
in lifespan for said items might result as well due to increased stress.
An ABSOLUTE minimum operating voltage is very near 4.0V. Rx's typically
use a 3.3V regulator which requires an additional 0.7V to power itself,
resulting in the 4.0V minimum. In application, however, it is typical for
performance to become severely degraded as power falls under 4.3V DC.
Ref: http://www.futaba-rc.com/faq/faq-receivers.html

Based on this I would suggest that 4.4v DC (under load) is the lowest voltage for a receiver to work, period.
I would also suggest to you that since today's packs are wired in series (4 times 1.2 equals 4.8) that if a cell
dies, the whole pack is shot.

Again, thanks for your response.