I'm confused because I don't know what the T8 is (don't have them in Canada). What kind of light is in there? I'm thinking some sort of LED because the second post says it doesn't get very hot, but I am concerned because OP said they wanted to warm up the enclosure...

Is it possible to post a picture? (Or is there one online somewhere as an example?)

My corn used to wedge herself in between the lip of her glass vive and the lid, when she could actually fit! She would just down as well when she had enough. I wouldn't worry about it - unless the light produces some kind of heat! Or if you notice your BP squirming and showing signs of stress while trying to get down.