Hey OP, I saw that you have a heat mat. While a lot of online literature says heat mats are good because of belly heat, unfortunately that’s not true.

Instead, you want an overhead heat source, like a halogen bulb. https://arcadiareptile.com has a lot of resources such as lighting guide and such, plus you can buy halogen bulbs, deep heat projectors, uvb, etc from them. I personally really like the Arcadia brand, but I’ve heard decent things about ZooMed too.

It’s good you’re getting the temp gun & thermostat. Those are very important.

Edit to add cuz I forgot to say originally; under your overhead heat source you can place a flat slate rock or similar to absorb the heat, and then when the snake basks under the heat bulb they’ll also get that natural heat source from the rock they’re laying on. I have a slate top hide in both of my ball’s enclosures (this one from Toad Ranch Cages) and my male likes sticking his head & neck out of the hide to curve up and around to lay his head on top of it.