I have installed many of boot heaters over the years and there are many schools of thoughts on how to run the wires along with where to put the batteries. I mostly use Hotronics and my installations tend to be on the powerstrap verses the rear spine of the boot. I chose it use the powerstrap because when you mount on the spine, the heater wires more susceptible to damage from getting hit with the chair when getting on the lift. I was doing an install for Jed's mom and he brought along some Thermic Smartfit Clips (a universal clip) for the back of the boot to install the heaters. I mentioned that I prefer mounting the battery packs on the side then he showed me a little trick. The clip is designed to work with the battery pack vertical or with the pack 180* inside down. When you turn the battery pack 180* opposite, the wires aren't as susceptible to damage from getting hit with the chair. It is a little change that makes a big difference. While I still might continue using the powerstrap for many installations, it is not always an option now with some of the different strap designs, this is a viable alternative. Sorry, I should have take pictures.
Thanks to @Jed Peters for the suggestion.
Thanks to @Jed Peters for the suggestion.