I know several folks that run 2 ceramic heaters in their 30 footer when they are in the campground and they say it works quite well and saves on the propane. I think they run them mostly on low heat because of the wattage. Not sure about the current draw on the 30 amp travel trailers. But they said that is why they got the heaters with the variable heat switch.
2010 Jayco Quest G2(SOLD)
2014 Jayco Eagle 33.5RETS
2007 Ram 2500 5.9L Cummins(SOLD)
2015 Ram 2500 6.7L Cummins 4WD