I have a Heatilator E42 radiant fireplace. I would like to put a wood burning stove in front of it and use the existing 8" SL300 chimney (25'). Can I do this if I install a 6" liner in the SL300 pipe? The chimney is centrally located inside the house until the roof exit. Do I need to use an insulated 6" liner? Will it fit?