I am installing a Fisher Grandma Bear with an 8" flue collar on top. Can I insert 8" (outside diameter) double-wall pipe (6" inside diameter) over this flue collar? If not, do I need 10" pipe (8" inside diameter)? Do I need any special connector or adapter between the pipe and flue collar? I would like to use double wall pipe all the way up. The total length of the chimney will be about 16 feet.
![[Hearth.com] chimney install for Fisher Grandma Bear [Hearth.com] chimney install for Fisher Grandma Bear](https://www.hearth.com/talk/data/attachments/328/328472-b5b457a6e6de2804c07eb75b106326d1.jpg?hash=VNYNXF2OyX)