If you have the pad on the bottom, make sure there is ventilation to prevent overheating. I propped mine up with some bricks so lots of air flowed below. If it’s on the side, it should be ok. I use a heat control thermostat when I need to use heat mats.
should be fine. I would prop it up though like @MissSkittles said. I have one on the bottom of a tank I use for mine. I do have it sitting on a one inch high screen so that there is air flow below and so the pad is not on anything that I do not want damaged.