Ideally you want to be able to take everything out of the enclosure when doing the 'monthly' cleaning, which would be impossible with anything hot-glued into it.
This is why I think it's better to tape the thermostat under the UTH. If it is between UTH and glass and water is spilled in the enclosure the glass floor will cool down, the thermostat will read that temp, and the heat will stay on until the water has evaporated.