Put it on the heat tape and use a thermometer in the warm side of the bin (on the substrate) to adjust the heat tape so that it provides the target temp in the bin.
IE the thermostat probe on the heat tape for my pac gopher is set to 92 to achieve a warm side temp of 85 (decent gap between tape and cage bottom).
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11.14 L. getula californiae (Cal. King)
2.3 L. getula nigrita (MBK)
1.0 L. getula floridana (Brooksi)
1.1 Pantherophis guttatus guttatus (Corn)
0.1 Pituophis catenifer catenifer (Pacific gopher)
0.1 Heterodon nasicus nasicus (W Hognose)
4.2.14 Elgaria multicarinata multicarinata - (Cal. Alligator Lizard)