This is a great site. Thanks for sharing your knowledge. I've searched all over the net and can't find this one. I'm connecting an Englander woodstove with a 6" collar to a chimney with an 8" (inside diameter) clay thimble. I noticed that NFPA 211 requires the stovepipe to be inserted to the flue liner. I was going to use 6" stovepipe increased to 8" near the chimney, but 8" stovepipe is too big around to insert. I considered buying one of the 8" telescoping stovepipe sections and using the smaller diameter piece to slide into the thimble. Any suggestions?