Neapolitan (from Amsterdam), sorry for catching up on the thread so late (S! Omid), but you should alter the design a little. You show the center 5 bricks to be flat to the floor. That will make the integrity of the oven reliant upon the cladding. You should continue the arch, no matter how small an increment.
There is a smal increment, sadly the camera on the iPad does distort the True lines of the design.
I Did try to make the top of the dome as flat as possible since this seems to be tipical in the Design of the traditional Neapolitan ovens.
It was even pointed Out by Marco Parente on this forum.
But Yes I do wonder If it would colapse!
At the moment I am not planning to build It since I have no room in my appartement nor A save chimeny.
But I Will look for advice when this situation might change for the better!