What I do it use a product called "repti-carpet" or something like that, it's like green carpet with no backing. We have several sections of that so some can be washed / drying while the others are in use.

I put that on the bottom of the viv, the my temp probes gon on top of that (held in the place by the wires being threaded though holes in it. Substrate on top of that, hides positioned over the substate that is on top of the probes. Thermostats set to 82/92.

We also have a small CHE mounted above the enclosure, which is also connected to the warm side thermostat to keep ambients up.

I check with my IR gun to make sure belly temps are pretty much exactly 82/92F in the hides.

This way there is no way the snakes can burrow down the UHT's, or move the probes - works really well.