Morning all, I have a NBBD for 11 years and it has served me faithfully. But now it needs some tender love. I am going to make a new frame for it and put on some decent wheels as a start. I have been looking on line at the various different upgrades that have been done to this type of grill and I am probably do most if not all of these, seal the doors, baffle plates, fire bricks, extend the chimney down to the grill and perhaps reverse flow. While I was looking at all these different sites I came across Feldon's BBQ pit builders calculator. I punched in the sizes for my grill and the recommended opening is 25in sq. I went out and checked the opening in my smoker and it is coming in depending on my math between 51 and 60in sq. For this reason I was planning on lowering the fire box by about 4-5in to reduce this opening. I am going to use a piece of 3/8 x 12 x 14 plate to fill the resulting holes and give a bit of stability to the joint. I was also going to raise the height of the opening from the fire box by about 1 1/2in to encourage the smoke/heat to travel straight into the smoke box under the baffle plates. Does anyone see any major flaw with what I am proposing? Other than the pain and time involved in doing it. Thanks in advance. Karl.