I decided to build masonry offset smoker inside. Smoke chamber is 1 meter by 2 meter rectangle Fire chamber is roughly one third offset to right with air intake opening far right air flows right to left out of fire chamber into rectangle smoke chamber with air exiting far left. chimney is 10 in diameter for 25 inches in height then right turn and left turn out the wall all of it at 10 in diameter. So I am exiting smoke chamber at 10 inch diameter and 25 inch height then passing through the wall and outside at 10 inch diameter. Then I have to go straight up for 40 feet due to apartments above the restaurant\smoker. what diameter for the vertical 40 ft vent? tips for successful airflow?