Working voltage, resting voltage, and the 50 percent rule

50% might be the limit anyway, since the real lower limit is whether you can still run your electric toaster in the morning without setting off the inverter's low voltage alarm.

With only a pair of 6s that might be at 75% SOC and with four 6s, 50% SOC. Or if you want, you can make your set-up so it would not alarm till lower than 50%, if your RV's size and layout will allow for that.

(Assumes no running the gen or any engine to "support" the voltage for that inverter time)