tub size issues???

I got ready to tub my snakes this weekend and have been working with temp/humidity control, and I have a problem.

They're going to be kept in an area where the ambient temp varies rather significantly depending on what season we're in.

I got 66qt tubs- which I think may be the problem. At first, I tried the tubs with a med. UTH. Humidity was fine, but temp would skyrocket, even with the thermostat set for 85. The probe on the UTH would hit 85, but the inside of the tub would hit 95 or 100 depending on time of day. I figured my problem wasn't enough air holes, so I added more. Then, I lost too much humidity.

So, I patched a role of holes in the tub, and I got a small UTH. Now, I can't get enough heat in the tub. The UTH will hit 90, but the opposite side of the tub will only hit 75.

Am I right that this is a tub size issue? Maybe my tub is too tall? I wanted a 45 or 50qt tub, but I haven't been able to find one, and I've been all over. Suggestions?

Simple fix.. messure the temp in the tub not on the UTH.. When to tub temp goes up the thermostat goes down when the tub temp goes down the thermostat goes up.. Most heating issues can be solved but proper probe placement..

Ahhh, but I am measuring the temp in the tub. That's why I can say that the temp in the tub is currently 77.4 and the temp on the UTH is 102.5.