chimney size for cement block hotel pan setup.

[snowman]

Hi all. I built an arch with cement blocks holding 3 pans the long narrow way. My thimble and pipe are 5". Too small? Center pan got the hottest. My fire box is 24" x 24".I did get all 3 boiling but not consistently.any info would be most helpful.

[Cabin]

Hi all. I built an arch with cement blocks holding 3 pans the long narrow way. My thimble and pipe are 5". Too small? Center pan got the hottest. My fire box is 24" x 24".I did get all 3 boiling but not consistently.any info would be most helpful. I made one this year and am see the same problem. I made it so the flames have to get past an inch opening before it gets to the chimney(8 inch in my case). With the damper closed I can get 3 of my 4 pans boiling, I use the first as a preheater. My fire box is 18X20x14. I am playing with changing the height of the fire box to get the flames closer to the first pan.