I have mine in CB 70 plastic tubs, with Ultra Therm pads underneath. Before I got a T.Stat for them, I used to check the temps on the floor of the tubs with an infrared RZilla thermometer ($10 on Ebay). Now, those pads rarely overheat, but if my BPs had moved their hides directly over it & were in there, it would get to 95-97 in there. I would immediately move things around until it was back to 95 in the hot spot.

It's probably too hot if you can't stand to leave your hand on that warmest spot for a while.