You were told right for the tank size sometimes when having issues even smaller maybe recommended, this is not about what you think snake happiness (that's called anthropomorphism and is often a common mistake with new owners)
Will BP making sure the animal is feeling secure is the most important part of proper husbandry, if the animal moves around a lot during the day there might be an issue.
Also the hide should not be larger, the hide should be tight like a shell on a turtle's back.
What is the size in grams or oz or your BP?
What are your temps?
How often do you handle your BP?
What prey size do you offer?