Thanks for the reply. The damper I made in the past was a bit too airtight. It would put the fire out, until I made some adjustments to it. My shop dimensions calculate to needing 52,000 BTU for the lower level. I hope to heat the upper level next year, and it's only 50% of the space, so 75,000 BTU would be good. I'm torn between a smaller amount of water and quicker recovery, or a larger reserve and longer, but less often burns. I've been happy with the past 2 stoves, but I think it may have been overkill, especially with your calculations as gallons per BTUs.
I'm using a 75 cfm draft fan going in through the door, one Taco 007 pump, and the stack will be 6" out the top, with a baffle in the top of the firebox. As for pump supply outlet, I had my last one off the bottom area, but changed it after a few months, and got a warmer supply, with no apparent changes to the stove, as it was drawing off the top of the firebox. I would keep at least 12" of water over the top of the firebox, and have it set on enough slope, to have any air in the top of the stove, going straight to the vent pipe. With the vent pipe I used, I would rarely have to add any water. I'd keep a check on it, and keep the temperature low, and increase as the ambient temperature started to drop. Keeping it running during the summer for heating my potable water, I'd keep the stove temperature @130 degrees.
I'll do some more calculations, and check back in. THANKS!!