I've spent more time in bear country in Westys than other vehicles, but the
only time I ever had a bear actually break into my car (in Yosemite) was in
a 2-dr. coupe when I was in a tent nearby.  That was back when I was a
student and it cost a lot of money to fix up that car again.  Since then,
I've been religious about keeping food or anything recognizable as a food
container (bags, coolers, etc.) out of sight and I avoid odiferous foods
such as bacon when I'm going to camp in an area where bear breakins are
known.

I actually think you have less chance of getting  broken into in a Westy
than most other vehicles, since bear breakins usually occur at night. 
People in a tent a few feet away don't discourage a bear one bit, but
people actually sleeping in the vehicle probably do.  At least, I've never
actually had a bear try to enter a Westy when I was in it, but I've chased
more than a few away from unoccupied cars parked in or near a campground. 
When you're backpacking or other circumstances when you're going to have to
leave your vehicle unoccupied overnight, try to plan to leave it with as
little food present as possible.  Above all, leave the inside clean and
uncluttered looking so there is no evidence of food.  

The absolute worst place is Camp Curry in Yosemite.  Throngs of people, all
of them camping, but their tents are usually hundreds of yards from their
car.  The bears in Yosemite have learned to break into cars from their
parents, who learned it from their parents, etc.  Other places which have
bears such as Yellowstone, Glacier, and Alaska don't seem to have nearly
the breakin problems that Yosemite does.  

This is just one guy's opinion based on some experience, but I think if you
keep your vehicle clean and uncluttered, avoid odiferous foods in bear
country, and don't leave it unoccupied overnight with food present in
Yosemite, you'll be OK.

Bill