I recently bought a pellet stove. I need to vent it through my existing fireplace chimney. Problem is, the chimney services my fireplace on the first floor as well as a bedroom on the second floor. The pellet stove sets in the center of the fireplace but the chimney is off centered approx. 12". I need to use a straight pipe into the fireplace, a 45 degree elbow up into the chimney, then I run into the offset part of the chimney. Can I use another 45 degree elbow to continue up the remainder of the chimney? Or could I possibly use a piece of flex pipe?