I found a copy of the Duo-Therm Service Manual
on-line at Bryant RV.
On page 3, it says that the air-conditioner is a 115 VAC device and the proper operating range is between 103 and 126.5 VAC, but that voltage should be taken at the unit power supply leads (to include the voltage drop of the house wiring going to it). Remember that from the campground power pedestal, where you may be measuring voltage, there's voltage drop across about 30' of 10AWG cable to the breaker box, plus that on maybe 15'-20' of 12AWG cable from the breaker box to the AC unit.
What it doesn't say is that any AC voltage measurement should be taken with a quality RMS voltage meter.
Whether I'd run the air-conditioner with pedestal voltage as low as 108VAC RMS would really depend on whether I could get through the night reasonably comfortably with the Fantastic Vents.
Of course, if you have two Honda EU2000s in the truck bed, to get you through the night until you can find another campground, low campground voltage isn't an issue!