"-I'll think about a hardware solution for the bench seat.}

I've considered this also.� The local serious hardware store (not just a Lowe's or HoDeport) likely has a vast assortment of lockage types.� Say, two or three key-matched gun-cabinet-type latches that�install across the seat base and latch with a quarter turn.� They would not rattle like a hasp and padlock�would and might be nearly invisible, thus not provoking curiosity.� Lots of possibilities.
�
Stephen