That's a good way to go patternwannabe. At what point is a voltage regulator needed too? I really don't know that answer, but somewhere in that 6-volt(5-cell) pack range I think I've heard of some running regulators/matchboxes.
I have that same Edge w/Moki 1.80. I run a single 4.8v(1400mh) pack on a R127FM Rx, with no prob...matter of fact, I have same set-up in 3 large planes. Good luck finding it though, and be safe.