If I leave the dimmer at full and didn't adjust anything my tank will hit 84f in which its the same if I just plugged the UTH into the wall directly. I really got the dimmer to beable to turn it down if the temps raised to much for some reason and to turn it down at night. And I think with the thermostat even if it is set at lets say 85f and your matt is only able to hit an airtemp of 82f, your still only going to get 82f even if it is set at 85f. I guess you would need to make sure your heat source could produce the heat your setting the thermostat at. That's my guess on that question and if im wrong someone please correct me, im still learning and trying to make sense of some stuff myself. for the mounting on the bottom I know a lot always say don't it put there it can burn them. While I agree with this to some degree I wouldn't put on the bottom for the reason these are burrowing frogs, and when they get warm they will go under the substrate to cool off and get away from the heat. If his substrate is warm he wont be able to regulate his body temperature properly and it wonder why he cant cool off.