In reply to jhw:
yes it's possible. you just need to be a bit creative.
Fill your panniers (side and top if you've got them).
attach tent or other bulky things to the rack/topbox using a bungee net or similar (this will take up your passenger seat then)
wear a rucksack if you need to.
you can also get a small tank bag that you put a cord around the handlebars and then there's a strong magnet in the bag