How do you use an open bottom humid hide???

Anyway, the humid hide is a Zilla rock lair, and it's small and dark so it would be hard for me to beat that. I think I'll just leave it for now and if I notice he has issues with it, I'll change it. I measured the temp and it's only like 83* inside the rock lair, when I want 90* in the warm hide where he spends most of his time.