there is another way,no cutting , no vents , no screwed in doorway fans;
first a bit of background, the unit is in one room and the rooms that are sepearated from it do not get as much heat due to walls being in the way and only doorways to allow heated air in, problem is , these rooms already have cooler air in them ,and since cooler air is heavier than warmer air , the warm air finds it difficult to "root out" the colder air.
its trying ,but its not efficient bacause of the weight difference and only (usually) one way in. a natural convection current wants to build but there is not enough force to make it happen (unless you help it, right)
place a small desktop fan on the floor just inside the doorway in the cooler room , aim it at the stove why at the stove you ask, simple, the air is coolest near the floor, that air we want moving towards the stove to be heated, also, that air is heavier, so moving that air is more easily done.
now , here's the way this trick works, as the cooler air is drawn out of the room down low, the heated air then is pulled into the cooler room right over the top of the cool air that is leaving. hence warming the room.
as i said this occurs naturally as well, this is how to test it; take a match , or lighter or candle, stand in the doorway , light your flame and hold it up high in the door, the flame will lean into the cooler room , being pushed by the heated air graduallly going in there, now lower the flame near the floor , the flame bends toward the warmer room as the cool air is gradually leaving the room. all the fan does is assist the current in doing what physics makes it do anyway.
now, only run the fan on its lowest setting ,and keep it aimed low , not up in the air to disturb the heated flow leaving the stove. give it an hour or so and you will see the temperature in the cooler room rising at a decent rate , be advised now , that this wont happen instantly , but it will happen much faster than if no assistance is used.
i use this trick when we get home from out of town or somthing when the pellet stove has been shut down and the house is cool, it helps a lot , the house warms back up more rapidly by far than if i do not do this.
hope this helps ya