On my Dx8 using a 2 cell LiPo the manufacturers warning is set to 6.4 v so that is 3.2 v per cell.
9.6 v would be for a 3 cell Tx LiPo.
LiPo's can go down to 3.0 v per cell before death but you never want to get that close.
At first I figured 3.2 v per cell would be OK but found some info that LiPo's don't like being drained that low.
So 9.6 v is out and 10 or 10.2 is hard on a LiPo.
10.5 v
Is what I found to be a good low voltage to set the Tx LiPo warning to.
I run the Rhino 2620mAh 3S tx LiPo on my 9XR.