Couple of questions: In the drawing on the right, I'm not sure I understand what "Divide Areas 80-20 / 90-10" means. According to Feldon's calculator if I size my firebox at 100% it calls for almost 4 openings 1.5" wide and 3" high. Would that be 3 of them at the bottom and one of them at the top? Or should I change the calculator to the actual size of the FB and use those dimensions to size the intake openings? That comes out to almost 5 - 2"X3" openings. So would that be 3 on the bottom and two on the top?