Could you post a picture of your chimney too?
How have the sheet metal doors worked? When they're closed, how is the fire getting air? Or are you finding that it can idle enough with the doors closed every so often because there's enough heat still to keep the boil going?
Just curious. Thinking of how I can upgrade my block arch this summer. I went from a block arch with no real chimney to a bigger one with a chimney this year, but it's all cinder block and no fire brick. I know it can crack and I'm losing tons of heat but it's lasted so far.
MVIMG_20190313_140405.jpg
2017 - 5 gravity taps, 2 pan block arch, 1gallon syrup
2019 - 18 gravity taps, 5 pan block arch, 4gallons
2020 - 25 gravity taps, 2x5 arch, RB10 kit, 7 gallons
2021 - 25 gravity, 75 on 3/16, 2x5 arch, RO10 kit, 13 gallons
2022 - 85(?) on 3/16 tubing