We use small 1500 watt space heaters for main heat and then set the onboard units so that they only kick on when the space heaters cannot keep up. It sounds cheesey but it keeps you from getting hot air blown on you and temps stay very stable.

We use them on the boat and we have a toy hauler camper we use in the winter months and do the same thing.

I do hate the narrow heat/cool deadband because when the wife cranks down the temp and it gets too cold changes the setpoint to bring on heat so I have to turn the unit off and let temp gradually rise.