Hi harold,
You know very well my stance on the "cheap heat (NOT)" system. Too bad you choose to NOT share your extensive factual knowledge and real life experience of the system with others.
I have done more than one "back yard" experiment to show how many watts are needed to heat a class C. Where are your results?
My needs are pretty much identical with anyone who uses their RV in extreme cold. You do not do that, and it is great that you don't have to, because the system might just fall short of the needs.
For example last night at 1 a.m. the campground power went off. First my inverter picked up the load, then after that the furnace cut in. It was -23 C (-9.4 f) outside. That would be enough to freeze up the entire rv quite quickly, if I had no "fail over" in place. Because I do, I slept right through the night.