Thanks for the replies to all.
What problems do you see with the Feldon calculations on the reverse flow? I respect everyones opinion and since this is my first reverse flow build would like to consider all options.
I used a 275 gal fuel oil tank for the reverse flow cooking chamber and have the first set of removable shelves 3.5" above the reverse flow plate and the second set of shelves 10" above the first. There is 10" above the second set of shelves to the top of the door opening of the tank. This leaves alot of 'dead air space' above the door opening--- what is your opinion of welding in a 'ceiling' to lower the smoke and heat closer to the cooking surface?
What is the advantages / disadvantages of the cooking chamber chimney placement on top versus near the food grate?
According to the Feldon calculator I have made the firebox that is 114% of the recommended size. I have two adjustable air intakes - one on the bottom (below the grate) and one on the side - both sized according to the calculator. My thinking was to use the bottom air intake for starting the fire and getting the temperature up, then close the bottom vent and open the side air intake for drawing the air across the fire into the cook chamber.
The firebox opening to the area under the reverse flow plate is 116% of the recommended size. The opening at the end of the of the reverse plate into the cook chamber is the same as the firebox opening.