I called Zoo Med to see if they had any input on the placement of a probe between the glass and the UTH. I'm not putting this out there to say anyone is wrong, I realize there are many ways of doing things and that everyone has to make a judgement based on their unique circumstances and sense of appropriateness vs what the manufacturer recommends but I did think it would be worth sharing what I was told just for perspective. the person I was passed on to through zoo meds customer service phone tree seemed relatively technically savvy. they stated that the UTH is engineered to be fully and evenly adhered to the glass, so that the glass can distribute the heat without excessive heat build up anywhere on the UTH. they mentioned that when the UTH traps a large air bubble under it, that heat encapsulation can occur, changing the heat distribution from what the materials were designed for. they said that eventually, this can lead to a runaway thermal situation and be a fire hazard. in terms of placing the probe between the glass and the UTH, they said that the probe is not designed to handle that much direct heat and that they have seen this lead to a melted probe. they didn't recommend having it even within direct contact of the glass above the heater, inside the tank. I figure that to the extent to which I am going to go outside the manufacturers recommendations, that I would at least like to know what problems to look out for.

from a previous conversation with them two years ago, with respect to mounting the heater on a piece of glass and placing the entire heater inside the enclosure they said that they could not recommend that but that if I was going to do it, that the lowest wattage heater was the least likely to cause thermal runaway issues. in my current 20 gallon, I went with two of the smallest heaters, side by side on a 1/4 inch piece of glass that I had cut and edges ground. the tank is heavily insulated, the thermostat probe is placed on top of the substrate showing a temp of about 88-90 f. the cool end of the tank is at about 78. our two BP's go from one hide to the other as needed and are eating and shedding well. the enclosed system is holding a constant humidity of 50-60% pretty well with some holes for ventilation and occasional misting. The person I talked with on the phone two days ago said that the only documented cases of snakes getting burned from UTH's that they knew of were cases where the rest of the tank was much too cold and that the snake couldn't regulate it's temperature properly, huddling too close to the UTH heater out of desperation. Again, I'm not saying this is the end all be all only correct information, or even that it is correct information, I'm just passing on what I've been told from one source.