I can't imagine not being able to get a good warm side temp with a UTH and a tub. What are you using to measure those temps? If it's a digital thermometer with a probe, where do you have the probe? I just know that unregulated a UTH will get to over 115F on the warm side. If everything is setup properly, then it could just be a faulty UTH. Pics would definitely help I think. I know that many people use newspaper without hide boxes....just make sure there is some crumpled up paper on each side if you are not using hides.....although I would always recommend using identical hides with a bp.