The HP in our MH is not designed to be the primary heat source. It is useful when its in the 50s and you want to take the chill out of the air. When its colder than that, its time for the LP furnace. The furnace, besides heating the inside, also has heat ducts to the dump valves and water pump, and provides heat around the holding tanks.
IMHO, trying to make the HP do something it wasn't designed for (primary heat in cold cold weather), is unneeded. The LP furnace was designed for that. I had a HP for years at home. It was designed (with electric backup coils) to be the primary heat source. But when temps were in the 30s or below, all you really had was an electric furnace. I celebrated the day we finally had access to gas and could replace the HP with an efficient gas furnace.
2012 Forest River Sunseeker 2300 Chevy