I'll probably bump the heater installation thread, but I'll mention here that I'm working on a different method to install the heater in my new liner/footbed setup I'm using this season. In the past I always installed the heating elements in the footbed, but it was always was a hassle and created limitations in what I could do to the setup long-term (removal of the footbed for further modification, due to how I ran the cable inside of the rear spine of the ZipFit liners).
This time around I'm going to try to install the heating element in the liner, not the footbed. I'm going to mount the element to the "roof" of the liner toe box (above the toes) and cover it with a piece of self-stick Cambrelle fabric. I am going to run the cable inside of the ZipFit tongue. Since the Zip has a tongue bladder for the OMfit material, there is an "area" between the bladder and the hard plastic on the front of the tongue. I need to cut a slot opening into the bottom of the tongue to feed the cable in, but once that's done, it should be relatively simple to feed the cable up the tongue and out of the top where there is already an opening/slot where the bladder "feeding tubes" pop out.
This idea came to me on the ski lift, where I noticed that when I'm on the lift, with my skis hanging off my feet, that the tops of my feet/toes are pressed into the roof of the boot. This is also the time when I want the heat the most, not when I'm actively skiing down the mountain. So I think this will work, but this is definitely going to be a guinea pig moment... I don't recall ever seeing anything about installing heating elements in the roof of the liner toe box.