One basking spot will work if it's large enough for a dragon to bask their entire body under completely to get an even bask. UVB should be right next to the basking light for most intense UVB along with highest temps. In very large enclosures you can sometimes add a second basking spot that is just heat with no UVB but you need enough space to provide a gradient. You still want areas with little to no UVB and daytime temps around 70-80.
I have an older version of the herpstat2. One probe sits on the cool side floor and the other is sitting on the basking surface with a rubber band. The wire is zip tied and anchored to the wall along the back corner. I have one bulb set to pulse and it's a heat projector that comes on at night if the temps drop out of 70-73 range that is controlled by the cool side probe. The basking light is controlled by the basking site probe and is set to be 100-103 and dim as needed.
I just got a herpstat 1 and I’m having issues getting my surface temps where they need to be. The probe measures air temperature correct? I have a 4x2x2 Enclosure, and I have the basking light sitting on top of the mesh top. He has a log to allow him to climb higher and closer to the light. At the highest, he is still at least 8 inches away.
What temp do you have your thermostat set to to keep the surface temps in the rig range?