Questioning what size pipe I should have from the back of my wood stove to the chimney. The back of my stove is 7". I put a stainless steel liner in my chimney, 6". What size should I use going to the liner? Neck it down at the stove to 6" or run 7" to where it goes through the wall and my 6" liner begins? Coming from the stove it consists of 2 90° and about 36" of pipe. Thank you!