Hello, brand new owner of a Sinoloan Milk Snake here with a quick question.
Everyone talks about temp ranges but not where to measure them or whether to prioritize air temp or surface basking temp.

I bought an UTH but don't have a thermostat yet so it's off.
Currently using a 40-50W bulb during day on a dimmer and a nano 40W ceramic at night. Mostly worried about not overheating bc we are temporarily using a 10gal while traveling & that seems the greater risk with colubrids. Switching to at least a 20long next week.
The uth was reaching 112-121 surface temp on the felt liner I bought so I turned that sucker off but probably plan to go that route later bc snake likes to burrow so much.
The bulbs are working well but if I aim for air temp(mid to upper placement of probe) on the hot side at say 84 the basking surface under it is over 90. If I aim for a surface temp of say 85 the air on the hot side is 75-80ish. Cool side is perfect both ways.
Which is better?

That said the little guy is spending his time happily buried in the Aspen no where near the basking area no matter the temp.
Separate question- can't find anywhere how people heat Really Useful Boxes... Are they using only UTHs or do some modify a mesh hole in the lid for a bulb?
Thank you in advance!