I'm having a bit of trouble with this, too. Everyone says that a thermostat/rheostat is essential for the UTH, so I got two lamp dimmers - one for the UTH, one for my heat lamp. I don't really know how much I'll be using the one for the UTH though... on full blast, it seems I'm just BARELY warm enough on the warm side! So I ended up placing my heat lamp over the hot spot, too.

Does anyone else do this?