I struggled with getting the humidity right in my tubs too, first it was too humid then i got carried away with the drill and the humidity was way too low -___- the humidity is about 30% in my apt, pretty low, but with the right amount of holes I find that I can use newspaper as substrate without a problem. For my 32qt sterilite tub, I have about 40 holes all around and my humidity is pretty steady at 66%. Word of advice, make sure the holes aren't too big! I used a drillbit that was way too big, and made way too many holes on my first tub. I suppose that tub will go to one of my corns.. waste not =) Soldering iron is definitely the way to go, and start out with 20 holes or so because you can always add more.