ARS 5040 Keeping Tub Temps Consistent

So I decided because my collection is growing I would invest in a real rack system and decided on the ARS 5040. And to use my DIY rack to quarantine any new animals. It's currently in my living room with forced air. Temp in the house stays at about 75-80 deg. I got the herpstat2 and set the top 5 levels and bottom 5 levels to hot spots at 88 deg. Eventually (this week and the upcoming weekend) I'm going to frame off a smaller room and have a permanent snake room. Top to bottom is good but the problem I'm having is the tubs on the ends are pretty consistant 88-90 on hot spot and 79-82 on cool sides. But the tubs in the in the middle are a little warmer, around 90-92 hot and 81-84 on the cool. Using a temp gun to get measurments of bare tub without substrate. I know its an open air rack but is there anyway to get middle and side tubs to run the same? Was considering maybe foam insulation on the sides. Or should I just try to find a happy median and let it vary a small amount between tubs? Any opinions/suggestions would be much appreciated.

Thanks,
Sean

Personally, I wouldn't worry about that small amount variance. I would actually just move around the animals based on how they sit in the tubs.

The ones that hang out at the front more, move them to the cooler tubs. They can then move to the back if they so wish.

But again, I wouldn't worry about it.