This has been explored in some depth recently in another thread. If you do a google search for radiant heat flooring it will probably be near the top of the list. My recollection is that it isn't very feasible due to limited floor space and the need for large amounts of hot liquid to heat the system.
I use a 110v oil-filled radiator type heater when I have shore power. It heats the Safari nicely, and has a timer and thermostat built in. Power consumption on the midrange setting is 1500
watts which is all that's needed down to the 30's.
For situations without shore power I'm leaning toward a vented radiant propane heater, or possibly a small woodstove, or a combination of the two. I don't like the forced air furnaces I've seen so far and most are just plain too loud and powerful for a 19' metal box.
I also have a niced soft carpet runner for those cold-floor-mornings. Best investment so far.
Rich the Viking