Winter use??

As long as you keep the fresh water tank and water lines above freezing, not the TT interior necessarily. Is this tank in an enclosed underbelly? Does the furnace discharge hot air into the underbelly?

Exterior unheated waste tanks in freezing weather require you to do the non conformist methods.
You must leave your waste valves open, grade your waste line so there is no trap. Always use enough water to carry the waste through the hose. Double flush the commode. Never 'trickle' water to keep your lines from freezing as that means a very slow flow through the waste hose that will freeze there then back up into your waste tanks.
Be certain the camps sewer pipes are below freeze depth so that they do not freeze and back up.
Theres more, but these are proven.

www.ultraheat.com

All my tanks are exposed underneath and work fine with the heat pads.

In sub-freezing weather, we used our Class C all the time. We flushed the toilet after use with antifreeze*; and used bottled water for toothbrushing, etc; followed by a splash of antifreeze down the drain (left the freshwater system winterized) What a lot of people are forgetting is that there are low-point drain tubes; plus the valves for the wastewater system (and possibly an outdoor shower), that can still freeze.

* We DID have one trip home in single-digit temps where we used a "luggable loo" portapotty because urine will freeze at about 28 degrees

Deb and Ed M wrote:
In sub-freezing weather, we used our Class C all the time. We flushed the toilet after use with antifreeze*; and used bottled water for toothbrushing, etc; followed by a splash of antifreeze down the drain (left the freshwater system winterized)

This is what we do for the first few days getting from New England to Florida in January when the temps often are around 20 degrees in the morning.

Those heating devices appear to be geared towards heating waste tanks and drain lines, not fresh water. I think there is an implied assumption that the fresh water tank is inside the coach, which is not true in my situation but may work well for the OP.

Dave