We have a 2014 Southwind 32 VS and are on our first Winter trip from Ontario to Floridan this coach.
We left home with it still winterized as I wasn't sure how well the basement heat would work and did not want to risk any frozen pipes.
Prior to leaving, I removed the front cold air grill inside the coach and located 1-4" air duct going from the furnace to a hole in the floor into the basement.
I pulled the duct back out of the hole, ran the furnace and there was good air flow coming out of the duct, then replaced it back in position.
You may want to check to ensure your duct is in place to direct heat into the basement.
I placed 2 remote temperature sensors in the basement, 1 in the wet bay next to the fresh water tank and 1 in the utility bay next to the dump valve, the display were placed on the doghouse so I could monitor while driving.
During sub freezing days, the furnace kept both bays in the 38-45F range.
I now feel confident that we could de-winterize at home and travel with a working water system.