Thomas, Isn't it amazing how you can make such a significant leading statement as that, and be totally ignored by the willfully ignorant? Ever feel like you're stuck making a movie with the Three Stooges? Exhaust openings: One thing the backyard casters and black smiths both worry over is how large to make the exhaust openings on there equipment. Too small and you have high back pressure killing burner performance; too large and you can't get enough heat to stay within the equipme