Well, I took lessons from my experience in the HVAC industry.... worked for 9 years on assembly of industrial water chillers - Air cooled and water cooled. Most of that time was spent on brazing (with better equipment than I've got now ). I kinda wish I had that torch with me.... hehe...

As far as the heat exchangers go, it really was just part of the challenge. I'm eager to see how well it works.

Its taking me a bit of time to build given that I'm more carefully planning the build while I go. I'm trying to stay true to the drawing I produced, though there will be some deviations. Any wild deviations from that drawing are planned and remodeled before I move forward. When I run into problems I stop work and consider alternatives. The last time I was a bit too hasty and made some critical errors... No need to be in a rush and mess something up...