No duck tape it breaks down under temps. Aluminum tape (HVAC or automotive sections) Check the temps on it, the tape should be at least 150ºF
The temps will change once you add the UTH. Ambient temps are a bit more complex than it may seem.
First how are you measuring the ambient temps? the Accurite? If so that will work check both low and high the critical one is low at or near the substrate. The thing to remember that most don't think of is that snakes have a very very long lung. It runs over half the body and the ambient temp the air temps are what the snake breaths and the lung will heat or cool the core temp. A high ambient combined with the thermal gain from the skin the core can be warmer than expected.
An ambient temp in the low 80s is about right but even in the high 70s will be fine but too high and the snake simply cannot cool down. Thermal regulation is exactly that regulation it requires a shift in temps low to high, which seems simple on paper but isn't as easy as it seems. for example a snake that sits on the cool side all the time the logical thing is to reduce the cool side temps. Right? Not always the warm side maybe producing a warm air current (something to think about how is the air going to move inside the enclosure?) that is heating the ambient temps while the substrate stays cool, causing higher than expected core temps in the animal.
So far things sound about right but the UTH will change the whole works anyway so don't fret too much until it is fully on line and give it a day to 'settle' in. On/Off systems need a bit more time to stabilize as they work on an average of high / lows. Not my fav type, read 'control freak' here. Whilst waiting I really recommend running the uth wide open for a hour or more and check the MAXED out temps. I like to know how far the temps will run, I try to match heating power with the max possible temps and try to get them so a max run will produce less than terminal temps no higher than 100ºF (95-7 preferably) if I can. I'll sometimes add a spacer to manage it.
