If you put it inside and the probe gets cool down (water dish being spilled, BP peeing large amount, moved by the animal) the temperature will shoot up possibly leading to a burn, this is why it is essential that the probe is secured directly on the heat source where nothing can affect it. After that all you have to do is play around until you find the right setting that allows you to achieve optimum temps.

I am not for making thing 100% permanent inside or outside the enclosure as things might need to get moved, or re-purposed or even throughly cleaned, and you will find out that 99% of keepers keep the probe OUTSIDE