Actually yes I doi had the same problem. Replace the plastic on top with tin foil and cover pretty much the whole top except in the area of the light. Also what kind of substrate are u using? I would use cypress as that's the only substrate I can find that keeps my glass tanks humidity over 40. Usually my tanks are between 45-60%. Also you want your hot side about 90-92degrees and the cooler side between 82-84 degrees and the foil will help a lot with that.
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1.0 normal bp- Blitz
1.0 Nicaraguan boa- Gavin
0.1 Red Tail Boa- Tara