setup questions

i just bought an 11 x 17" uth for my 70 gal glass tank. the brand is cobra heat mats. there were safety precautions on the packaging saying that its unsafe to have substrate above the heater because it may block the heat from coming out. i normally use about 1/2" of aspen bedding.
does anyone have some suggestions on what i should do with it? i was thinking of just placing the heater against the side of the tank.
my main reason for switching heating equipment is to block off the top of the hot side to keep my humidity up. i have a serious problem with keeping humidity in the winter months.
any suggestions would be great. thanks!

I have read many times that Aspen holds and transfers heat very well. I myself use a Zoo Med UTH I dont know if there is any diff. in the two. But honestly if you are using a glass tank the only concern I see is getting a stress crack if you should have any kind of water spill (from waterdish) right above the pad. Even a tiny crack can spread very quickly from heat exposure, and WILL result in replacing the tank.

I too use aspen, but make sure the probe is measuring the temperature of the class and uth. If the probe were place on top of the substrate and the animal burrowed it might be to hot. I have had not had a problem with any of my tanks. By covering a good portion of the top and misting the aspen daily my humidity level stays at a good range. Others with more experience can offer better advice as far as t-stat probe placement goes. Mine is in the tank held against the class using aquarium sealent and a small piece of wood to hold it against the glass. Make sure you do not cover the probe itself. Others feel it safer to place the t-stat probe directly on the UTH, between it and the class.