also,m make sure the wires inside are orderly. Just anything to make it not look a mess. I would say that if you are taking it on a plane to make certain that you use ide cable to make the insides look more professional. Also, no nicad/nimh batteries. They look WAY too similar to bombs. Litiums can resemble bombs too. In fact, if it is a power sipping portable like a noac/goac/aoac, then just power it with AAs. That way they can't confuse any batteries as bombs. Also, make sure it is not a ghetto looking portable. Make it look nice. Something like a cnc made case would pass off as professional, but a porry bondoed frankencase would look incredibly suspicious.
Sonyportablizer lost his atari portable because he made it in literally 4 hours and as a result it didn't look very nice.