Is there any sort of consensus on what diameter flue pipe to use?
Also, is there any reason you have to operate with the lid on? Can you just run the pipe up to the top of the can, take the lid off entirely, and put something like a BBQ grill on top of it?
4 in is what I usual see used. You would have to be careful using it as a grill as you are channeling the heat of a 36” Grill in a 4” pipe.