I used a small tankbag and a tailpack for all my touring and managed very well.
Only other advice I'd offer is if you're thinking about using a rucksack or backpack for long journeys, forget it. You'll be hot and sticky underneath it, it'll impair your mobility and generally be a pain in the @rse. One of the guys on the inaugural Eurotour had one and it spolit his trip. Best to get the bike to carry the load. Oxford stuff has straps and hanfles if you need to carry it around with you.
And don't forget to adjust your suspension if you're carrying heavy stuff (a heavy duty chain in the tailpack seriously affected the steering and I nearly ended up in a field
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