Any thoughts on possible problems of keeping the existing 5 inch liner in my chimney? Must be ancient but we pulled it out and it looks to be in good shape. No stove in the house when we purchased it. Fireplace/chimney in center of house. Looking to purchase a stove with a 6 inch intake: Hearthstone Homestead, Hearthstone Morgan insert, VC Intrepid II, VC Resolute Acclaim, Regency i2400 or VC medium insert. Thanks for your help.