Hey guys, I've got a question about the height of my fire box. I'm going to build the fire box on the side of my old 3-burner Weber Spirit grill. I want it to look as "stock" and unmodified as possible. The grill itself has volume measurements of 20" tall x 24" length x 17" wide. The grill tapers towards the bottom to 14 3/4" wide below the burners, so I set that for my fire box width. The frame that holds the grill also comes out to hold a side table. That part comes out 13 1/2", so I set that for the fire box depth. Now, according to a calculator I downloaded, in order to roughly get 1/3 the size of the cooking chamber for the fire box, the height I chose was 6 3/4". Now is that tall enough to provide enough air underneath, while giving enough room for the fire? Here's a picture of what I'm basically dealing with: Sorry for the crude photoshop of the fire box.