To give you an idea of how a hide should be compare to a snake, imagine a turtle, well the snake hide should fit a snake like a shell fits a turtle. Hides need to be snug with all sides touching your BP's body.
To reduce stress 90% of it will be husbandry related. Assess your husbandry based on your snake size and do the necessary changes.
Also if you feed fuzzy mice those are too small as BP are started on hopper and quickly move through sizes.