I have a 2011 Sunseeker 2300, which sounds like the same floorplan with a different model designation as an earlier poster. RR corner queen with the water tank inside below the bed, gray and black tanks enclosed under the stepped up rear floor in the bed and bath areas. There are heat ducts running through from the furnace located right in front of the bed, under the refrigerator, including a perforated "leaky" one that passes through the back of the storage compartment where the water pump is and hot and cold PEX passes back into the house. All plumbing is on the inside, with the exception of the lines to the outside shower, which are tee'd off the bathroom sink lines at about the 3/4 point left rear. Even then, they only go "outside" right at the back of the fixture enclosure.
We've used the RV in low 20's weather overnight with no issues, just running the furnace. Most recently, that was just last month driving to Florida trying to get below the freeze line, having to give up at about MP140 I-95 SB when it was 11pm and still 150 to go to get above 32.
