I'm not invalidating your method. I think putting the probe in between the heat mat and enclosure works well. I just wanted to mention that in terms of gauging temperature it works either way. I'm not looking to discourage one or more methods. If in your experience it doesn't work well inside then that is fine. However I personally haven't experienced any flaws and find it works well.

I find that where to place the probe is quite a controversial subject and don't think any opinions or methods should be discouraged. As long as you achieve accurate/desired temperatures then continue doing what you're doing. Just offering other options.

If your bp happens to defecate/urinate inside its warm hide then simply move the probe elsewhere(while still remaining somewhere on top of the UTH as close to centre as possible) or change it up and wedge it in between. As long as it works for you.