Hi caotropheus, what a beast! and a lot of work ..but looking at the secondary air intake it looks like it is relying the wind to blow the hot air in for the secondary burn..my thinking here is to return the pipe ends back into the fire box at an angle of 45% or so.. and then back out side the fire box for the air.. the new pipes at 45% inside the fire will become very hot pulling in more air from outside.. because hot air in the pipe rises pushing hot air into the top of the fire giving a better second burn..;)