From what I've seen/experienced corns don't like temperatures that high. I'd say 85-88 range for the highest temp in the tank. But like everything, everyone will always have different opinions so there really is no right answer. Do what you think is best and your snake will let you know if there is a problem. Just be sure to catch that problem

Also to make him feel more secure, you can put duct tape around the bottom edge of the tank. That way it might make him feel better that "no one can see him." I did this with my ball and he bucked up really well.