I've got a large water bowl in a 40 gallon long tank, situated halfway over a large UTH. I use cypress mulch, which is quite moist in my opinion for substrate... My humidities are running in the 50's during the day. Much of the screen top is covered, and there is a basking lamp on the other end that is aimed at a fake desert stone hide that helps warm the other end of the tank during the day. My relative humidity can rise towards 80% at night when the light is out. Using a herpstat 4 for data now.

I'm new to this so dont take me as an authority.. just a data point.