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I wouldn't ever use a heater on the back with anything. You should cover the back of the socket with dielectric grease, and cover it with neoprene. You should also fill the socket with grease, and the slug should be filled with grease, then a piece of neoprene should be put in.
I like the vr-zone insulation guide, so I coat a large area around the socket (how large of an area is dependent on how powerful the chiller is) with silicone spray and a layer of seal string or armaflex.
Many people like to use spray insulation on wb's, but I have not tried that, on my mcw50-t I have a layer of seal string, and 2 layers of armaflex.
The res, tubing, block, mobo all need to be insulated (if the pump is inline and not submerged it needs to be insulated as well). This is not done so much as protect your components, but it is meant to maximize the performance of the chiller. Some people sacrifice performance, and don't insulate their wb's and lines, and mount their mobos upside down, but seems kind of dangerous, and a waste of cooling.