Hi coalstoves, I didn't hear anything in the plans you had for measuring the draft. As Greg stated you need a barometric damper before the chimney, the hand adjustable type that you currently have installed will cause the static pressure in the stove to become positive and should not be used on a stoker stove in my opinion. Not enough draft inside the stove itself means that the hot gases will be pushed through the hopper, thus putting CO in the house.
Based on my experience with the Harman Mag Stokers you will need to install a barometric damper within three feet of the stove and also use a draft gauge to measure the draft in the stove pipe and the stove itself. Per the manual you will need a minimum .04 in the stove and .02 in the stove pipe. The little plate over the intake on the combustion blower is used to adjust the draft in the stove.
On the subject of efficiency, I found that setting the timer up to run the stove more like a hand stoker worked great for keeping the fire at a minimum burn without using the Tstat. I set the stoker stroke for maximum dots and ran the stoker motor for 2 minutes on and 15 minutes off, with the distribution fan off delay set for max so it never shut off. I also plugged the combustion fan into the power outlet near the stove and let it run all the time. Set up like that the stove could run for 4 to 6 days on one hopper of coal and it kept my 800 sq ft poorly insulated garage at 55 to 65* during 30* outside temps. When it got colder outside I would just increase the on time to up to 5 minutes and leave everything else the same. I found that using the Tstat requires some patience to get it set up right, the manual has some good pointers on how to do this.
I am getting ready to try out the Coaltrol on my Harman that I am selling so I will let you know how it works out. I already use one on the Alaska I have in the house and it has performed flawlessly all last year. It keeps the house to within 1* of the set point.
Sorry for the long post, hope this helps.