Hi, I have a VC Defiant 1975 Flexburn about 6 years old. I live in a drafty old log cabin. The previous owner ran 5' of 6" single wall from the flu adapter to the ceiling and then 10' of double wall 6" pipe from the roof to the cap. I have always had problems with smoldering fires and ash in the room when reloading. Sometimes it will puff back. I am getting my roof redone, so now is the opportunity to change to 8" all the way up. I can't go higher than a 15' chimney on the small roof. Should I spend the money and convert to 8" all the way up (flu collar to cap at 15') or will it not improve the stove's operation? Thank you.