My rack is almost done! thermostat+probe questions and general feedback requested.

[C&H Exotic Morphs]

Lastly my biggest question is where should I attach the probe? I can do it directly to the heat tape but im not sure thats the exact temperature that will translate to the inside of the tub where the pythons will lay. Do i need to measure the actual inside of the tub and adjust from there or do I just set the prob and assume the inside will be the same?

First, nice DIY rack.
As far as probe placement you want to attach it directly to the heat tape. You will then have to adjust your thermostat setting to get the correct temps in the tubs. The thermostat temp setting will usually be higher then what the actual hot spot in the tub will be.