Hi,
I know that 4.8V is low for LiIon and LiPol battery. (For LiIon is minimum 3.0V) I wanted to tell you, that you can be sure, that ignition will work, if voltage goes down bellow 6V (I know that this is wery bad for battery, bat model or plane is more expensive than battery). High voltage part and processor can run down to 4.8V as I wrote fomerly. There is one problem if you are using a servo for choke. A stabiliser for servo start working from 5.5V.