RE: ATX and LiFE
2S Li-Fe packs are ok with ATX receivers and servos
The Sd-10G voltage range is not really a match for Li-Fe cells. Their nominal voltage is the voltage our radio starts sounding the low-voltage alarm.
The SD-10G was really made for 2S lipo if you want to run something other than the stock 6 cell battery or similar NiMH, NiCD or Eneloops.
Similarly, the RDS8000 is made for 8 cells NiMH. a 3 Cell lipo is ok. A 3 cell A123 is a little low and a 4 cell A123 is really too high.