On the subject of chimneys, what is the purpose of having an adjustment capability on the lid of the chimney? Say if i have it all the way up or somewhere in the middle?
I don't think the chimney has much purpose while under fire, but when you have a good bed of embers you can close the chimney all the way and bake bread or similar. It will maintain temp for an hour or two, depending on how big of a pile your embers are.
half an hour later, the oven is ready at 405C.
I know they promote 25-30 minutes preheat time, but I prefer giving it a full hour at least to saturate the hearth with heat. I encourage you to give it a try, you may get better charring.
Looks like your having fun, and that pizza looks great to me