How was your efficiency?
I have a large stainless steel stockpot that I use for a mash/lauter tun. It is magnetic stainless so I direct fire it with an induction cooker. It ramps at around 1.5 F per minute. The pot is wrapped in several layers of aluminized "bubble wrap".
My manifold is 3/4 copper tubing that I cut LOTS of slots in with a Dremel tool. Is roughly square with two cross pieces in the middle besides the tubing that makes up the square. One of the middle pieces has a T in it that connects it to the fitting in the side of the pot
Here are the components. 4 elbows, 5 T's , 3 long tubes, and 6 + 2 short tubes. Two of the sides consist each of elbow, short tube, T, short tube, T, short tube, elbow. These are permanently soldered up. To use I put the 3 long tube into the opening on one of the side pieces (two elbows, two T's) and then the 4th cross piece which consists of two short tubes with a T in the middle, and to the other side of the T, a really short tube, a 45 elbow, and enough tube to attach to the kettle fitting and center the manifold in the pot. Then the other soldered up side is attached.
It holds together pretty well just pressed into place, but I've taken to tying a string around it to hold it together. It then comes partially apart after use for ease of cleaning.