Very cool. I am looking at using bubba as well, cheap and heavy duty. My only decision now is between the 30 gal and 55 gal barrels. I figure I will start with the 30 gal, and can up grade to a 55 gal BK if I want to stretch into nano territory (based on my calculations, I could still press out a 1.078 1 bbl batch with the 30 gal MLT). However, your idea of the 42 gal MLT might be a great compromise, plus the wider diameter might make it more efficient.
I will be soldering in 1" tri ferrules for my in/out ports, and 1.5" ferrules for the electric elements, trying to eliminate all threads for a sanitary design (again, pretty much just case I want to creep my way into nano). Right now I am planning on TC sight glasses, but if brewtroller comes out with a simpler computer user interface by the time I get this project off the ground, I may go that route as well. Right now I am spending so much time on the hardware, I really don't want to delve into the BT software, but we'll see.
Thanks again for the post, I will be keeping up to see how everything goes!