Gaerlan's site explains how to pack 20"-wheeled Dahons: http://www.gaerlan.com/dahon/pack.htm This may apply to the Yeah, but you would have a bit more room in the suitcase due to the 16" wheels. The frame may not be much smaller since the axle-to-axle distance should be similar.

The Samsonite Oyster is a hard-shell, fairly reasonably-priced suitcase that is often used. Someone earlier mentioned a deal at eBags.com (around US$60 using Google Checkout): Oyster29

Hard-shell suitcases can still be compressed when a dozen other suitcases are piled on top of it, so adding some flanged posts between the top and bottom (in the short dimension of the suitcase) helps protect against crushing the wheels. These posts also help hold things in place.

You may want pack photos of how to repack the bike if the security folks open the bag.

Good luck, -Paul