I was inspecting the 20 foot chimney that I was going to install the pellet stove in and found some thing unexpected. There is an 8 inch round flue all the way down to the top of the fireplace where it breaks trough and converts to a stove pipe. The old flue (13 x 13 ) was filled and blocked off. Do you think I need to pull a liner or just covert from 3 down to the 6" pipe that comes out of the bottom of the fire box? Pulling the liner would be easy but saving 200 bucks means I get a ton of pellets.