After a few months of inactivity, I finally got down to getting the boiler finished. I used 1-1/4 black pipe for all the near boiler piping which was relatively easy. I've had a couple of fires with it and it works as expected (good news). There are still a few things I need to deal with: overheat zone (power failure), proper pipe supports and insulation, and the control wiring to integrate everything nicely with the gas boiler. The piping follows the Tarm Large Square Tank layout.
Sorry for the sideways photos, I've tried everything I can think of fix that.
Sorry for the sideways photos, I've tried everything I can think of fix that.