Good evening. I’m getting ready to install my jotul f3 in a small cabin. I have a cathedral ceiling with no attic space. Area between rafters will be spray foam and finished ceiling will tongue and groove. From what I’ve been seeing, I need single wall from stove to cathedral support box then double wall from there? Do I need a support box? How do I know what size support box to buy? What’s the code for my height after exiting roof? Thank you in advance for any help you can give.