A probe to a tstat can be between the uth and the glass, that way it can't be moved. The probe to the thermometer needs to be inside so you have the correct interior surface temp. The substrate needs to be thin over the uth because it will insulate and not allow the heat all the way through. Many use a IR temp gun to get the surface temp.
For bulbs I like using lamp stands. I keep a cold home and over my forty gallon tank I have this set up.
With the stand you can raise it and lower it to get the desired temperature. You can't see it but most of my screen is covered to trap heat and humidity.
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