The only way I actually found to really heat the Sterilite totes is by putting it on top of my boa cage under her radiant heat panel but even that only heats it to around 88-90 degrees. The best ones I found to heat were the Rubbermaids. Seems they are thinner on the bottom so easier for heat to get through. I'm using the 45 gallon Rubbermaid Roughneck tote with a 30-40 gallon Zoo Med UTH on a lamp dimmer set to around 1/4 power and I hit around 100 degrees at the hottest spot on the bottom of the tote. Just be aware if you use that tote, you will need to run a strip of packing tape around the top about an inch or 2 from the top cause the little ones can climb the sides of that tote but it's really easy to heat and its big enough to house a huge colony. I got about 150 females in there with babies and nymphs of all sizes all over, plus way too many males but I can't bring myself to give them a burial at sea aka toilet and my beardie isn't big enough to eat adults yet. Thermometer should be fine. I use a temp gun since that's pretty much what I check all my reptiles with anyways.
Thank for your help. I bought a 14g rubbermaid tote (my colony is only 35 total right now) and the small UTH I had is getting the hottest spot on the bottom between 93 and 101