i'm not sure i'm completely understanding your temps. are you saying that the temp is 90 degrees in the hide, with the paper towels being moist, but when they dry the temp goes up to 98? and on the floor of the cage the temp is 98?

as long as the leo cannot get under the paper towel you want to measure the temperature on top of it. are you using a glass tank and is the uth stuck to the bottom of it? you want there to be some air circulation between the uth and the glass--you can elevate the tank higher off of the uth to bring the temps down (i used to use blocks of wood for this).