I'm somewhat surprised at the lack of discussion on this. I know I'm really looking forward to it. I bet a bunch will weigh in after to nitpick the tests, results, and general clothing choices of the the participants. (The frequency response effects of black tshirts is well documented at heavy metal concerts)Did my first primitive mockup of a heat exchanger. Don't have a lathe, so I chucked tubing in a 1/2 drill and used a belt sander. It fits pretty good. I was really just going for the dimension, however. I'm going to call around tomorrow to find somebody with a lathe.