The best deterrent I know of under this circumstance - parking at a
trail head, is to project the impression the vehicle belongs to a
hardcore hunter.

An empty bow arrow or rifle rack works well in a prominent location. The
problem is most rifles won't quite fit in the width of the rear window
because of the closet cabinet.

I still haven't figure how to fit a bow arrow rack there and able to
keep the factory curtain functional. :-)

I know a bow arrow hunter who prominently leave a couple of arrows on
the front seat or the dash when he parks in the wilderness. He drives a
big ass American 3 1/2 ton pickup truck though.

- Vince

http://gipsyflies.home.comcast.net
1989 Vanagon GL Camper
1993 Mazda Miata (for sale)
1996 Land Rover Discovery
2005 Mini Cooper S