White Lipped Python enclosure question

[Tchambers]

So I have been keeping Lloyd my white lipped python in an approximately 40x16x16 enclosure that I built because everyone seems to say they need to be kept in large enclosures. However he spends all day every day on the cool side of the cage. I have three hides on the cage, 2 on the warm side and 1 on the cool. He seems to be happy and healthy...well I wouldn't say happy because you know how WTP's are haha but he eats for me and is very active at night. I'm just worried he isn't getting the heat he needs because he spends all day on the cool side. Should I put him in something smaller until he grows or just keep him in here? He's still a pretty small guy. About 3 feet or so. Let me know what you guys keep your WTP's in. Thanks!