After measuring for a liner, the length is 31' from the top of the chimney to the thimble opening. The original tile is 8x12, or 7x11. Not sure because the liner is weathered at the top being over 50 years old. I couldn't get a paint can down the liner, so I figure I will need a 5.5" liner. With the length of the chimney I think that will be okay. Theres one thing I'm not sure about. The length from the center of the chimney to the front of the thimble is 32". I don't think a tee will work there. On top of that I have ductwork about 2' in front of the opening of the chimney. Any ideas on what to do? I was going to go with a flex liner, but the local amish sell rigid stainless liners that are 22 gauge if I remember right that are very reasonable. If I went rigid I think 6" would fit okay. Any ideas on what to do? I don't have room for an insulation blanket, so I was going to pour thermix, or vermiculite down to insulate the liner. I really don't want to bust out the old liner.