Ok, number one for future reference: To get stable humidity in a glass tank you have to foil or plexi treat the screen top.

As for the RBI cage, first off you have to place the Herpstat probe UNDER the cage in the slot provided. It has to measure against the heat source. Now, you say a Radiant Heat Panel is installed...but most RBIs I know of come with flexwatt belly heat. At any rate, the t-stat probe has to be placed against the heat source.

Two, do not use the t-stat as a thermometer. Often times the setting on the herpstat is going to be higher than the inside temps. Use the Acurite backed up by the temp gun to get the temps where you want them regardless of what the stat has to be set to. If the stat reads 102 but the warm side reads 92...so be it.

I found, when I had an RBI 4x2 cage, that the temps were not really even on the warm side. You just have to find a good range.