I've had numerous packages opened by US customs -
 they reseal it with this ugly green tape that 
says its been inspected so it's pretty 
obvious :) As far as additional duty fees I 
would imagine it would depend on what country 
you are in - in the US there are no customs/duty 
charges for personal importation so thats not a 
concern but that isn't the case everywhere. It 
might not be the cels, either..I once had DVD's 
seized because customs thought they were 
bootlegs and not legit R2 discs, took a while to 
get that straightened out. Good luck!