I was told I spent enough on my supplies so a dome lid is out of the question. I want one grate to cook thicker meaters like butt brisket and a second grate to cook just ribs, Since I've read the first grate should be 24 inches from the fire box grate how high should the firebox be in order to not snuff it out with ash and how low does the top grate need to be in order to put butts and briskets without cresting the top of the barrel?