An old thread, but maybe someone will read it down the road. If you have an S&S bike (which it sounds like you do), I highly recommend the soft backpack style case. We have both the hard and soft cases, and have used both styles when flying with our touring tandem internationally. Hands-down the soft case is much easier to work with, and you can fit a LOT of extra stuff (clothing and other soft things) in the outside pockets, which then serve as very good padding. Even though we've flown with two soft cases each way (it's a tandem) on multiple trips, we've never had any issues. I think the extra padding provided by the clothing really helps cushion the interior contents. It's an additional cost, but you could also consider getting an extra S&S soft case (assuming you already have a hard case) and pack your extra stuff in that. It's easy to put the soft case inside the hard case for storage at the start of your tour, leaving you only one suitcase to store (nice if you are storing at an airport that charges you per day, per bag). Our hard case has been gathering dust for a while, as the soft cases are also lighter.
On a tour last year with my S&S single bike I was able to fit the bike, racks, tent, sleeping bag, and other items all in the S&S soft bag. I carried on my rear panniers (clipped together as others have suggested so they were officially "one piece") with my clothes and other stuff. Nowadays staying within the 50 pound weight limit is the real challenge, and it's even less on many intra-European flights.