I've had cases where the staples actually _RIPPED_ the
cel during transport!  even a major jar could cause
such an event depending on the thickness of the acetate!

So whenever I get a cel like that I scan it (a very good very high quality scan...) so I have an image of it lined
up correctly... and then I remove the staple to protect
the cel (besides... when stapled to a background there
is a chance of the cel getting stuck to the background...
not so good... -_-)...

Then I put the background and the cel into their own
little bag and tape the bags together ^_^ (baggies
protect cel so you can use cheap tape ^_^)