Another project with a good group of buddies from work. Building 5 indentical trailer mounted 250 gallon tank cookers with insulated fireboxes. We been tossing around a few numbers and wanted opinions. Fb- 28x28x28. 2" insulated with rock wool. Stack- plenum mounted, halfway between rf plate and top of chamber, 6" id x24 The major question we have is the half moon dimensions for the firebox.. Using the recommended numbers from Feldons yielded a weird size. Experts please weigh in. Tanks are the only thing set in stone. 5 tanks, 30" x7.5'