Alright so i got a 300 gallon smoker that was already made. i did the calculations on the calculator for size of FB and size of chimney. The firebox is at about 76 percent of the preferred size according to the calculator. i am having trouble because the chamber is getting too hot. i have a couple splits going and i cant get a spot on their thats not over 240. Should i get a sheet of steel and block some of the opening to the chamber from the firebox like a damper?