An electric blanket is much more effective than hot water bottles. You can also add a "Stay Longer" connection and add 1 or 2 100# LP bottles. There are tons of YouTube videos on adding the connection and also another ton on tips and tricks for staying warm.
Kelly and Jerry Powell with Halo (Lethal White Aussie), Nash the Rat Terrorist, and now Reid, the "Brindle we have no idea puppy"
2020 Grand Design Solitude 390RK-R