Nice setup so far. But I would've went with belly heat though.. People heat plastic tubs all the time with their flexwatt/UTH's. As long as it's regulated it should be fine. I would ditch the thermometers you have in there and go with digital thermometers and a digital hygrometer. Wal Mart isn't the only place you can get it, there's online sources too. Go here for the Acu-Rite, they're pretty cheap:

http://www.partshelf.com/acu00891.html

That hide will do fine for a hatchling BP. It will start to get too small once the BP reaches 400-450 grams. Just get another one for the other side and you'll do fine for now.