I have a pit calc that works very well. I oversize fire boxes for reverse flow as well as the box to chamber hole and exhaust. It gives the option to go hotter.
Looks good so far but why go with red brick? Use fire bricks to avoid off gassing and reflect heat instead of holding heat. My last build is insulated with 2" and 1.25" fire bricks. You can pm me if you want pointers on it. My build is way more efficient and runs much cooler on the outside because of the bricks.
Cooking for the love of it.