Do you have heated tile floors? We find that with our previous 04 40' Allure, and now our 07 45' Magna, that we can stay comfortable with a single 1500W portable heater, and the heated tile floor cranked up to high. This into the mid 30's. In the AM, we may also turn on the AquaHot heating zones to pump up the temps if needed in the hours of getting up and moving around. Usually less 30-45 mins, then we turn it off again, and the combo of floor heat and portable heater are more then enough. If we need to get going early, and are taking showers. We'll augment the AquaHeat's Electric Element (Not needed as much in the 07 Magna as the 04 Allure, as the 07 Magna has dual electric elements.), by adding 'Diesel' burner heating to the mix. (Which, is the highest BTU available in these applications.).
We do use other heat gain (Sun and Cold) deterrents:
-Cushions in the Fantastic Fan Vents
-Window covers closed at night
-Outside Windshield Cover on
-And in temps say 30F or below, we use curtain rods to add insulation protection in the shower's solar dome.
And of course, emergency supplies of scotch strategically placed around the coach
Sedona is great this time of year. Hope you enjoy it, and have a blast!!