If you go to big it will stop up the air flow CG's Fire boxes are two small as it is I know I have one been cooking on it for 6 yrs. you can go 12.5 X 16 X 4 burn time is dependent on cook temp. If you want long burn times Build a UDS That CG will cook real good on Splits that is why it is Called STICK BURNER They aint meant to run on charcoal.
I never met a Cow that I didn't like with a little Salt & Pepper! Certified PORK-A-HOLIC