I too just switched to the heat cables. I was using heating pads like most people but don't really like the idea of a heating pad being on in my house 24/7.
The heat cables, I did like in a post here and cut squares of galvanized metal, measured to where they would cover half of the bottom of the tote. I then zig zagged the heat cable back and fourth across the sheet metal, kind of like in an S pattern, fastening it to the metal with electrical tape. Keep in mind when ordering or buying your heat cable, that there is a big section of the heat cable that is "Cold solder" and never does provide heat. For instance, the heat cable I bought was a 11.5' 15watt cable. The first 6' or so of the cable is cold solder, so really, only about 5 feet of the cable is providing heat.
I've got two of these 11.5' cables set up on the sheet metal like explained, plugged into a Rheostat which allows me to control the heat should it get too hot. This is controlling two totes of my colony.
Once you're able to view pics, this is the post I got the idea from for the heat cable:
viewtopic.php?f=76&t=92865&st=0&sk=t&sd=a&hilit=heat+cable
Here's a pic of a rheostat: