I am going to start with some data to compare stack temp and stove temp in various places to get an idea of heat transfer to the stove . If I know the temperature of the surface and the surface area along with the value of steel in my case I think I should get a pretty good idea of the btu output. Another idea I had is to record the heat rise in the room with a stable stove and stack temps. If i take xxx number of cubic feet of air and raise it 5 degrees in xx number of minutes I should be able to calculate the number of btus it would take to do that then just correct for one hour. These are ideas I am thinking about and may present a problem but might make some sense in the end also. I am also making the assumption that if the stack and skin temperature stays the same then the btu output from the fire is the same, again with a fully warmed up stove. My biggest problem is the wood quality But have a couple of dozen splits I know are premo seasoned 3 years oak and was saving for next week as we are going to have some nights in single digits though will intentionally run the furnace some to make sure I don't freeze any pipes in the walkout part of my basement. Oh and i can close off the room the stove is is and it is small at 11X17. Any ideas to make a better starting point fire away!