De-duplication and hidden block management could always bite you.
Attempting to physically destroy the device will just make people try harder to find what you are hiding.
An effective approach is to fill the drive with legal but embarrassing porn, and do a sloppy job of deleting it. The pseudo-random nature of video will avoid block de-duplication, very little of the previous contents will remain on the hidden blocks, and anyone forensically examining the drive will stop looking after they "find" the deleted porn.
Sometimes letting people "win" is the best way to succeed.