Hi Sarah, great to hear from you!
First of all, I like the way you've set up his table, with the pieces of wood, etc. so that he has to work his way around things in his table -- looks really nice.
Regarding the probe (is it a thermometer or thermostat probe?). Also, I can't exactly tell from the photo, but have you tied the wire of the probe to something stiff (like a coathanger wire or something) and then projected it into the table? Is the probe above the substrate or is it buried in the substrate?
What you want is for the probe to be hanging from above, with the tip of the probe at about the same level as (or just above) Shelby's shell. So I would definitely raise the thermostat probe to just above the level of Shelby's shell, and that should be just fine, and you shouldn't need to adjust temperature or anything. To get it hanging under the lamp, I've occasionally taped a stick (or chopstick to be more accurate) to the wall of the table, projecting horizontally into the table, then I've wound the thermometer probe around that until it's near the centre of the circle of light and then let it hang down. Does that make sense? I've attached a photo where I wound a coat hanger around one of the uprights that supports the lamp and then stuck it out into the table and wound the wire of the probe around it and then let it hang down -- it's coming in from the left-hand side of the photo -- can you see it?
[attachment=0]m_DSC00892.jpg[/attachment]
I definitely wouldn't leave it in a place where he can bite it, as tortoises do have surprisingly powerful jaws (which you will know if he has ever nipped your finger or bitten your toe in the garden), and he could damage it.
If I've got the wrong end of the stick (lol or thermostat probe)
let me know and I'll try again.
I'm so glad that Shelby is doing well, and I remember that he had a great time outdoors last year, and hopefully this cold spell will end soon and all our tortoises can be outside in the sun again soon.
Best,
Nina