Can't tell if he'd fit..."maybe"? They do squish themselves thru openings when they want to...where does that go?
BTW, you might be able to rent a fiber optic mini-camera (to fit into such places before ripping out a wall) used by plumbers etc.
Got any bookshelves? they'll get into those, behind the books even...and drawers in desks or dressers...can usually enter from
underneath in the back, where there are gaps in the backing or from the floor.