I was a ranger for 8 years at yosemite.  The answer is YES.  The bears
won't bother going through the canvas though, the sheet metal is simple
enough.  In yosemite we only have little bitty black bears -- a big one
is still usually under 500 lbs.  I personally saw one casually rip the
door of a Chevy Suburban, because the guy left a soup can (full of pencils
and other crap) on the dash.  Bear left hungry.

There was a story -- ask around Yosemite and you'll probably still hear it,
about a bear on the Tioga road that only broke into beetles.  They are
pretty airtight, and this bear would merely jump up and down on the roof
a few times until the doors would pop open...

Bears are messy eaters, and they smell really bad.  They have very large
claws and are clumsy.  They seem to have no appreciation for upolstery.

Personally, I'd *never* leave any food in the camper.  "Food" to a bear
is relative, as well.  Deodorant, soap, garbage, toothpaste -- it's at
least as tasty as rotting squirrels and termites, their normal snack
choices.

Bears can read.  Honest.  They seem particularly fond of the word
"Coleman".  Cans look edible to bears (they seem to have no trouble eating
them!).  The can-on-the-dash in the Suburban was good for probably $3k
repairs...

If you've ever seen a dog perform any trick, be assured that a bear can
learn the same things even faster.  The rangers at any park will have
lots of stories to tell.  I used to go on for half an hour during campfire
programs.

malcolm