Hi Fleetwood,
Since there is only 30 amps of power at the pedestal it might be worse to do that because the smallest system CH makes draws more than 15 amps.
I'd recommend looking into having insulbright covers made for the windows, vents and skylights. I am assuming you are using vent cushions already to insulate.
If there is a 15 amp outlet on the pedestal, look into adding an auxiliary shore power cord. That would allow running a third electric heater.
Where I live sometimes 6000 watts of heat are needed.
I prefer to use small wattage heaters tucked away in unused spaces in the RV. I find oil filled are quiet and because they have a bit of thermal mass, I can load balance if need be, and the heater will "coast" for a few minutes.
Earlier in the thread I documented what I'm using for space heating, and freeze protection.
Consider adding an extend-a-stay fitting and renting a 100 or 200 pound tank from a propane supplier.