In matter to the flue vent, I think that a chimney installed on the front of the oven (landing area) could be more efficient than the one installed in the middle of the dome.
There are some relationships that are established along the times.
Speaking on dome ovens, the door aperture will be as high as 63% of the higher point of the dome. This is because this is the relationship that assures the best flue of the gases.
The fresh air enters by the lower surface of the door; feed the flames, runs on the hearth, climbs the rounded walls and returns to the higher surface of the open, where exits. This path guarantees the higher ratio of burning and heat transference to baked goods and dome hearth, walls and ceiling.
If the relationship is lower than 63%, the fresh air divides the entry with the combusted ones. If higher, there will be vortex in the higher surface of the dome, reducing the burning and breaking the flue of hot gases.
If the output (chimney) is on the middle of the oven, it is ease to figure that the flue of fresh air will go from the lower and middle surface of the door, heating through the embers and going directly to the exit, wasting hot gases and requiring a lot of combustion to obtain the required temperature conditions.
If using a front chimney, could be good to build a landing area or entry, where the chimney will be between the internal oven door and the exit of the landing area.
There is a lot of information along the web, to better clarify these points.
You could see a lot of pictures and information of my oven (along tons of better ones) on the site www.fornobravo.com
. You could search by pizzabrasil (that is me <g>) if you like.