RE: 4.8 V to 6.0 V
KW,
There is always the option of going to a higher capacity 4.8 volt battery.
I fly 4.8 volt 2,000 mAh batteries in my 40 size planes.
The only time I remember being shut down due to low battery was an
unusually long flying day.
Do check your voltages frequently and do it under load.
Good Luck,
KW_Counter