The box looks fine as long as all the measurements are correct. I wanted to ask you if those halo-type objects are on your box to deter HOSP. If so, I’d remove them until you have the first egg laid. It could be that those fixtures are keeping bluebirds away, too, but once they lay an egg, they are committed. That’s when you put up your sparrow spooker & immediately remove it once all have fledged so HOSP don’t start getting comfortable with it, but you may already know that.
Gin is more experienced than I am, but I just wanted to comment on the fixtures on & around your box.