I made a comment earlier about the chimney being on the inside of the oven and I thought it would loose alot of the heat. Well i can understand the theory of its heating the bricks that matters and the smoke doesn't, some ovens even have the chimney at the back so the smoke just rushes out, my thinking is of course you do not want a smoked filled oven but if you can keep a "ball of heat" at the top for as long as possible then that has to add to the radiated heat from the bricks? without ending up with smoky food.
For this reason the middle/front drop technique seems to be the best way to go.
The chimney just before the front arch means you should not get that "dirty front" from the smoke coming out over time.
I haven't decided on a brick or pipe chimney yet, there will be a pipe because of the place the oven is in but there may be a small brick chimney ontop of the front arch.
