I'm finally getting around to having the essential mods done to my OK Joe Longhorn. I am tired of rotating meat to cook evenly. I scored a large piece of 1/4" steel plate and will have a welder make a heat deflector and tuning plates. 1. How low below the grate is best for tuning plates? I want to maximize airflow through the chamber so I don't want them too low. 2. Since I will have to go to a welder to have this done, I am thinking of having him lower the stack too. Is grate level or below grate level best? If placed below, I would think the heat would bypass the meat altogether...right? 3. Lastly, would increasing the diameter stack from 3" to 4" help and would I need to lengthen it for better chimney effect (draw)? Thanks for the help.