Thanks for all the great info, all valid points .
My advantage is that I will only be staying in these conditions a night or two and then I'll take the rig back down to warmer temps around L.A. If I need to leave it on the mountain, I can winterize it in about 15 min.
It seldom gets in the single digits and if so, only for a few hours. During that time I will be inside with an electric heater and furnace if needed.
I did pull out the rear storage tray and noticed a "T" off the furnace ducting blowing into the basement storage. All tanks are enclosed and get the heat.
Although if I know its going to get that cold, I'll probably head for Malibu or Ventura.