I worked a little on it yesterday, cutting up the heating element, figuring the spacing and test fitting. No soldering was done. Here is what I did with a few pics.
The aluminum fins on the element are just pressed fit onto the 3/4" copper pipe. After measuring I separated the fins where I was going to cut just enough to slip a hacksaw in between them and cut.
I then removed just enough fins so that I have enough room to solder the Tees on. One side of the fins is flush but the other has four triangular shaped prongs that grip the pipe. Since the area of the pipe that is finned will only be around six inches I tried to keep as many of the fins as possible. I moved the last fin to the end of the pipe and bent the four prongs up out of the way and pushed the fin back with the rest.
I then test fit the pieces together. There will be three of the cooling elements in the keezer. Two will be connected to two taps each and the third will only be connected to the middle tap. When its done I will take temps of all of the taps and see if there is any temperature difference between single and double taps. The plastic compression fittings are similar to the shark bite ones. The 1/4" OD vinyl tubing squeezes perfectly through the fitting but I will try some SS tubing when it arrives.
Including the fittings the length of each element will only be around eight inches. I am guessing that the short length of the elements will be sufficient to cool the taps due to the surface area of the fins, cooling liquid and the relatively short vertical run of the pipe. If I need more cooling later I can always increase the length of the element.
The only issue I see so far is that it may be difficult soldering the Tees on due to how close the fins are.
For those concerned with how heavy this will be I will weigh each element when done and let you know the number is. I would guess that it will be right around the weight of one tile that people are attaching to their lids.