Sure this has been asked a truck load of times already..... at what point is a firebox too big? According to Daves calculator I will need a firebox with a minimum size of 4620 cubic inches. Tank is about 20" in diameter, best I can measure it in the dark. Don't want to end up using 10" logs, would like to have the firebox 18" deep. Just using 18" as a height ( just seemed like a good number) firebox size came out 6480 cubic inches, which is 140% of the suggested size. Will this be to big?