I went by the hearth store today looking to purchase material to reline the chimney. Talking with the sales/tech rep, he asked why I needed to reline the chimney. I told him I was currently using a 5' flex up threw the damper and thought It was better to go the whole length. HE TALKED ME OUT OF IT. He said It wasn't necessary with the Quad Castile so, SAVE your MONEY. Reading everything on this forum. I was trying to convince him it was necessary. I left with my money in my pocket. Has anyone tried it both ways and noticed any changes. Any pros or cons from any of you who install. Thanks Tony