I could easily do that Dave and thanks for the idea. I could drill with a 2 1/2" hole saw and I am thinking about using 4" pipe and sliding it over the hole. Although a 6" hole and pipe might make future damper maintenance a lot easier. Then I would need a 6" damper and 4" damper. My biggest concern is the exhaust pipe is right neat the smokehouse roof and fire wood. I would like to block the rain from it, but might need to use a 90° and make some kind f rain hood for the 90 opening.
TXDVR, I was going to use the flue pipe too, but them read about it being fairly brittle and it needs to be covered with brick for protection. So I did not use it for that. I assume you could hand make a damper for a flue pipe but imaging you'd have to drill it with a non-hammer drill to make a hole and extend that through the brick. As fragile as that flue pipe is, having a damper sounds like a problem to me. you might be able to make a slot with brick that is not mortared to the SH base and the flue not motared there also. Then a flat metal plate with a lip could be slide in there as a damper.
To make an exhaust, I am not sure they even make a Tee for that. Its made for each fired appliance to have it own chimney and not to share them. You'd have to use a chisel to make your own Tee. Plus then you wanted to run the SH hot, you'd need a damper for the exhaust or a cap for it.