Dialing in my new (to me) Grampa Bear

More air - are you running about a full turn until up to temp? Smaller splits on the bottom and load in all directions to get air through the splits?

8 feet of single wall pipe is technically the maximum on top vent stoves, (I have to look up where I saw that -their heat rating is also based on 8 foot ceiling) so you have a lot of heat extraction going on.
Since double wall pipe inside is required on rear vented models that are intended for through the wall installation, I'd use double wall over 8 feet of single wall pipe as well. (Page 7; A-2 of the III Manual) Page 7; (E) Adapter required on rear vent model Dura-Vent Part No. 8872 is required to connect double wall pipe to flue outlet on stove. The first manual doesn't address this type installation. This will raise your flue temp and the stronger draft will bring you up to temp quicker.

Dropping the baffle front a bit will allow more heat up possibly getting you closer to 350*+ stack temp. Decreasing efficiency until you get it set up right, or stay with the inefficient connector pipe set up without baffle.
Plus you have an elbow or T off the back, so it's not straight up like a top vent. Is it a solid elbow that can't leak any air in? Make sure there's no gaps in the pipe joints too. 3 screws minimum at each joint don't always seal up the joints. Don't be afraid to add more short 1/2" screws if there are gaps in the pipe joints. Every little bit may help!

Good, just make sure after 4 hours you have little to no smoke.
It's difficult to compare burns with outdoor temperature and pressures changing, so trying the same thing with damper 1/2 closed on another day may or may not show differences.

I think we could have a good stove nerd conversation !
Instead of opening air intakes, it may be more beneficial opening the damper more. That does the same thing as giving it more air, but at a higher velocity.
Without getting way technical, higher flue temp, higher air pressure, taller chimney, (to an extent) and LESS Resistance increases draft. The last variable, resistance is the flue shape and size, elbows, reducers, cap, and the variable damper. So that changes the velocity (slowing by adding resistance). The lowest pressure in the flue system is at the stove collar. The faster the flow, the lower the pressure creating a higher pressure differential at the intakes. The higher velocity coming in, increases turbulence created by baffle. Also forcing the burning gas mixture to make abrupt turns as it travels through the stove (the direction of loading) and air space between wood mixes the air better with the combustible gasses. This is what gives a better oxygen mix.
The baffle gives a cleaner burn due to higher temperatures in the combustion region. Temperature is the most important factor for complete combustion. Tests were done with electric heating elements on the stove sides so any temperature could be maintained irrespective of other conditions. Measuring the temperature in combustion region, total combustion air flow, ratio of secondary to primary air, moisture content of fuel, type and size of fuel, and pre-heating of secondary air (this is not secondary air admitted with tubes, only the air admitted above the fire). Of these variables the single most important factor was combustion region temperature. Completeness of combustion was assessed by measurements of carbon monoxide, total hydrocarbons, particulates, and smoke density. As long as the temperature of the combustion zone was 1100* f. or higher nearly complete combustion was achieved. So the baffle impedes outward heat flow affecting the flue temp slightly, not the resistance in the system.

johnstra said:

Coaly? Anybody?

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I had to sleep on those numbers
You didn't expect a simple answer did you?