Whatever your design for the shell, build a large hearth with a double flue to accommodate two fireboxes. One perhaps a high mass masonry heater for sustained temps and to keep the heat downstairs longer (radiant heat is omni-directional), and a smaller stove (cookstove?) for topping off and quick heat when needed. The best advice I've had is to design the main heating source for 2/3 to 3/4 of the maximum expected need and then top off with supplemental sources. That way the main heater will run efficiently most of the time and will not bake you out.
Ehouse
Ehouse
