We have had Ortliebs for past 9 years, which have been great for month long tours & camping, especially in wet weather. We use the same size front/back. Most of time we don't use the extra space, but when carrying a lot of food for camp or during extended times away from grocery stores or for cold weather clothing, the extra space is very useful. And... some type of frame pack is great for the empty middle space on tandems.
