With your gear the probe should be sandwiched. It is not relevant where it is it MUST NOT MOVE. I always recommend a failsafe to prevent any issues if it ever becomes dislodged. A child or dog ect. can move probes as well.
A probe can be safely used inside but there are a handful of criteria that needs to be in place first. The first being that the sandwich method fails to control temps with stability. I have very erratic interior temps and in some of mine I use interior placement when I used the described sandwich I got 10 degree shifts when we had days like to day 83ºF inside temps during the day and 65ºF temps over night the probe is not effected by the air sandwiched so the gain cannot be predicted.
The steps for safe interior placement,
PROPORTIONAL control, a t-stat with NO hysteresis
The probe (regardless) must not move the probe and wires must be firmly fixed and may not move at all. I use high strength hot melt and/or structural silicone.
There MUST me a failsafe on the uth to prevent it from reaching critical temps.
Low wattage heat sources need to be used as well that do not get hotter than 100ºF maxed out.
I would strongly recommend a herpstat with a mechanical relay that will shut down power to the heater if the probe suddenly goes cool.
If the probe becomes pulled the t-stat shuts down, if that fails the failsafe shuts down, if that fails the heat source stays below a burn temp anyway.
It can be safe but requires a great deal of extra work and money.
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