I don’t think you should be putting a baking tray on top of your driver. I would hate for you to kill your light over something so simpleSpeaking of heat mats folks, another option I have tried the past few germinations with success has been to put them on top of my lights! I added an insulation piece and then a small baking sheet on top of that. It minimizes the radiant heat from the light dramatically. You can add or remove some sort of fabric to raise or lower temps as needed. Then I put my seeds into some small jars, covered them with a towel and then covered with a darker material to make sure it is really dark.
Not saying it is better than a heat mat. It's just one less thing to use electricity. Hope that helps. I used to put them in a cupboard but it just never got warm enough.
Not to mention I think it voids the warranty. Just looking out for my friends!!! Happy growing !