LOL, when the light is brighter, it is lower, when it is darker, the temp is higher. The temp should be the same around the hide. so don't worry. You are doing everything right except for getting the temp to be good.
I know but if I can accomplish my goal with a heat pad and dimmer... then I would rather used a thermostat and flexwatt for racking.
again, a dimmer is only to be used temporary not for good, they are extremely unreliable and can still cause the temps to rise and fail completely. Dont worry about "racking" now, concentrate on keeping this snake happy and healthly.