Well, just to make sure I'm clear about my suggestion, I didn't mean another full-sized bag. I just meant a little one that hangs under the saddle. I find them more convenient for the kind of stuff you might need to pull out DURING a ride--tubes, levers, phone, keys. Otherwise you're constantly going into your backpack, which I find to be a pain. Plus it frees up backpack space.

Something like this or this.

If that was already clear... never mind...