Yes, you know, it my be overkill... I really don't know. I guess I'm still learning about this thing.
The first few firings I got very little heat out of it. Mostly they were very small fires to just help dry out the materials, since there's really a lot of moisture that accumulates in something like this during the construction process... with all the bricks and mortar and stuff. After finishing the chimney through the roof, and constructing the heated benches, I was finally able to put the fire into counterflow mode last weekend. It performed very well. I felt good heat through the doors , though the bricks were cool to the touch for the first few hours. And well after the first fire died down. The benches got warm. About six hours after the fire died down the bricks began to feel warm. It gave off a nice comfortable, radiant heat.
The second fire is when I was sold on it. The bricks were already pre-heated, so it got pretty darn hot pretty fast. I can't be more precise than that since I wasn't taking temperature readings or counting the minutes. It stayed very comfortably warm for an entire day. At no point was it too hot. I imagine if at any point it got too hot during the winter I could just open a few windows. I really don't like that feeling of being driven out of the house by a too hot stove.
But, as I say, I'm just learning how to live with this thing. So far, so good.
I've added a few more pictures of the chimney through the second floor and through the roof. It has three flues though only one is used by the masonry heater. One is maybe for a wood stove, and one is extra. I love the idea of having an extra flue available for some future idea.