I use inside and outside placements depending on the room the enclosure is in (the rooms that vary the most get inside placement my office varies 10-15º depending on what the sun is doing.)

Inside placement MUST be snake proof. I place the probe over the uth position a small blob goes down first and then I cover the whole probe and part way up the cord If it is a tank I'd also tack the cord into the corner as well. I completely cover the probe IT MUST not move.

I can't move on the outside either so it must be accident and pet (children proof as well) proof. Personally I always use a secondary T-stat failsafe for every enclosure. Also I'd recommend a 100% test (not if there is a snake inside !!!) run the heater unregulated for a few hours and find out what the maxed out temps are inside the enclosure. If you have wattage and enclosure and any spacers ect. set safely the inside temps will not be over 100ºF Snakes cannot digest at 100ºF but will not become burned and will be able to tolerate 100º for a while during some accident.