Hi Malum Argenteum!
I just noticed your post. Sorry for the delayed reply.
I've attached pics of the initial tank he was in and where the UTH was located. The UTH did cover 1/3 of the 10x20 tank. So that's a plus. And you can see the substrate depth. Also attached is the warped pad itself.
His new tank is a 20g long. It's a 30x12. Would a new heating pad sized 8x12 work for the new tank?
Reading the posts from you and Bogertophis, I too, am VERY thankful nothing detrimental has happened to my little guy!