AFAIK, a snake that spends his time doing nothing in his hide is a very happy snake. Sounds like all is well in his world. But, I tape sheets of paper on the left side of the enclosure, as well as the left third or so of the front and back. It lets in some light still, but gives them the impression that it's saver to come out because they're not totally exposed. I haven't done it with my BP, but it made the difference for a very skiddish milksnake barely brave enough to venture out for water.
Maybe some tall smooth rocks spaced out enough so that your snake could hide to an extent, but still be out in view.
Just ideas. No clue if it'll work for BP's; mine comes out as soon as the lights go off.