I have used a Defiance Parlor Stove for many years in heating my home. The clay lining in my chimney has cracked and a small part has fallen down, I do not know from what part of the chimney. The stove has an 8 inch stovepipe. The clay liner in the chimney is 8 x 12 inch. I am asking if I can use a 6 inch chimney liner or what other suggestions for lining my chimney.