Super nice setup, kudos !!!
I have also read somewhere that aluminium tape can mess with the electricity? Not sure if that is true, though..
If you want the heat tape nicely against the cage as well as insulated (and not touching anything the cage may be leaning against) you can get a sheet of that super thin styrofoam (or other thin insulating material, push it against the heat tape and then tape it to the cages really well. Even when I have heat tape under a cage, I like to have the exposed side insulated, unless its a stacked unit.
If the cage sits on a stand, table or plywood, I put s sheet of styrofoam between the cage/heat tape and whatever it is sitting on. Making sure the styrofoam is taped against the cage and has a little cutout for cable and probe to sit in. It keeps the probe securely against the heat tape without bending the styrofoam.