The heat pad on the side is better for Pacman Frogs. Not only is it much less likely to dry out the cocofiber, but it keep the Pacman Frog from getting burned. Pacman Frogs instictively burrow when they are trying to cool themselves. That is one of the big reasons the heater needs to go on the side.

p.s. if you have already stuck the heater on, it is best not to try to re-use it after you take it off. UTH have very delicate wires, so trying to reuse it can cause problems down the road.