It was a year or more ago that Horizon posted on there web site that you should be using 6V packs with there 2.4 systems to help with the brown out problem. I haven't been back to there site sense then so I'm not sure if it is still there or not? I'm still on 72 so I mix and match my battery packs according to the plane I'm setting up. In the real world I have never noticed the drain difference between 4.8 and 6 volt but it can be measured with meters and it is a fact, just nothing you will notice at the field.