This is an important issue cryptographers and security minded people often overlook: the strongest cryptography is irrelevant if it opens you to such social harassment. What we need is practical cryptography. I have found practical success by booting from an encrypted Linux partition that has absolutely nothing relevant on it, with a weak password I can always enter when requested by big guys with guns. Unbeknown to…
> It's impossible for any court forensic team, let alone an airport goon, to prove there is actually another partition inside the outer encrypted partition, unless you mount common volumes and cross-contaminate. An important caveat is to properly defragment the outer partition and fiddle with the offset and the size of the inner partition to avoid any conflicts, then avoid writing in the outer partition.
Customs staff typically don't know to prove there is, they just need reasonable suspicion to seize goods for further investigation. The fact you've booted into a 50GB partition on a 500GB disk may well be considered reasonable suspicion to seize the goods for the sake of further investigation.