We have heated our old rented farmhouse (with next to no insulation in the walls) with a woodstove for many years. The main floor (the only one we heat now) is 1450 square feet. The steel-cored RMH was installed in the living room this fall and (with a few modifications along the way) is keeping us warm in the coldest snowiest winter here for quite a few years.
At first, the living room (where the RMH is located) would get sweltering hot and the kitchen would be quite cool. But now, with a few minor modifications, we have fairly even heat throughout the main floor rooms. During our last really cold winter we were happy to live at 68F and temps would often drop into the 50's at night. But now, we "old folks" don't seem to be comfortable below 70F and the RMH is suiting us fine. Daytime inside temps lately have been 70-75 and morning temps have never dropped below 62F.
In the two pics below you can see 4 modifications I've made to our Steel RMH:
(1) I added 4" flexible plastic ducts to the top of the feed tube and cleanout end of the burn tube to draw colder air from the basement so we wouldn't be using warm air from the house. (This is also drying out and slightly warming a very humid basement!) Both metal ends of these tubes are just tight enough to be a "friction fit" but easily remove to add more wood or cleanout the ashes.
(2) Added a fan (standing on top of the mass) to blow on the barrel and this alone has drawn much more heat off the barrel and circulates it evenly through the main floor of the house. (this has seemed to make the draft stronger and overall temps of the system higher!) Thus the next two modifications...
(3) Added two small fans to blow cooler air from the floor onto the sides of the burn tube and
(4) Because temps in my flue were going up to 160-175F, I added an extra section to my total mass. This one is 5' long by 2' high and 9" wide. It is built around the stovepipe after it exits my main mass. The back side is a brick wall above the existing hearth, the front is a sheet of steel and the space is filled with rock, gravel and sand. It is now harvesting a little more heat and our flue now runs about 140-145F.