Not sure if this will help you out with your current set up, but putting foam board up on the sides and back of my rack raised my temp 3-4°. It was pretty open air, though, so the foam board helped keep the heat contained and stopped any air from moving through - it was a bit 'open air'. It might help stabilize your temps or it might do nothing. It's should be available at any craft store if you want to give it a try. http://elmers.com/product/detail/902015