Only a handful of families in Naples are qualified to build an authentic Neopolitan oven. And, you can only use special materials from that region. This is what you will find in researching some of the posts. However, to my knowledge, (and if I'm wrong I'm sure I'll be corrected) Marco has never built an oven. You mentioned the other forum, its full of oven builders of the DIY variety. Your time is better spent there for building details. Then, here is the spot to perfect your recipes. I built a barrel vault oven and I can make fantastic pizzas that cook in less than 2 minutes. Learning the characteristics of your particular oven will be more important than the exact details of size/shape.