I'm installing a QuadraFire Castile Pellet stove in a home with a dual flu masonry chimney. One flu 6x8 terminates into the living room wall 8 inch opening. It previously was connected to a Frankin Fireplace (free standing wood burner) then a Vigilant coal stove. Everyone I talk to insists on a 3 or 4 inch chimney limner. Quadra fire offers a 6 inch connector PN 812-3570. My thinking is this is to vent into a masonry chimney like mine. Comments welcome.