2 smaller UTH's will work fine but everyone here will emphasize the incredible importance of a control for a under tank heater. Even the ones by zoo med (I have two also) will sky rocket to 110 degrees plus without some sort of control, like a thermostat. The non-digital (dial gauges) are very unreliable. I have compared my dial gauges to my digital gauges many times and found them to be off by 7 degrees and 15 % humidity. You can purchase inexpensive digital gauges at walmart or a hardware store that measure two temperatures at once(so a UTH and the ambient temp of the tank) To help with humidity immediately I would suggest soaking some towels and ringing them out, then laying them atop the tank. This is what I do every 2 days and it keeps my humidity right around 60. When my bp is about to shed, I put some sphagnum moss in his tank to up the humidity to 70% (this can be purchased from a reptile store or even a gardening store) The level of substrate does not make a huge difference protecting your bp because he/she can simply burrow under it like mine does often.