Here's a pic of what I use for travel:
A Joe Rocket "Sport" tank bag (no longer a 'current' model, but is still available from some retailers -
here's one) and a
45L Ventura Bike Pack system The current kit comes with a 51L bag now. It retails for $375 (can be found online for less) and comes with brackets for interchangeable racks, a Sport Rack (normal looking luggage rack), Pack Rack (luggage rack with a tall loop for attaching Bike Packs) and the pack itself. The pack just slips over the loop on the rack and attaches with a couple of straps with buckles, making it quick and easy to install & remove the bag. The bag can be positioned on the forward side of the loop if you're riding solo, leaving the rack exposed for mounting more suff, or just to keep the weight forward. For 2-up duty, or if (like me) you like having the room to swing your leg over the seat, you can mount the pack on the back side of the loop on the rack. The interchangeable racks slip in/out of the backets and are locked in place with knurled screws and jambnuts. At least on the 2G B6/12, even the brackets can be removed in a couple of minutes if you don't want them on the bike. This setup does carry your luggage weight higher than saddle bags, but if you're travelling light and aren't packing heavy stuff, the CG difference isn't that great and this kind of setup will not rub against any painted parts, which is a plus for me.