After lots of research and looking around, I picked up the 40 liter First Gear Torrent Duffle bag. I took a 5 day trip (1300 miles) over Memorial Day weekend. It easily fit all of my clothing and stuff. It would handle a 7 day trip without problem. I packed some of my more clunky gear/shoes and rain suite in the F6B rear bags. I had room to spare.

The straps that came with the bag worked easily and perfectly when strapping it to my MP3Bike rear rack. I did need to unscrew my antenna.

I got caught in a powerful storm/micro burst in southern Minnesota on my return trip. The waterproof bag and bike both came through without any problem.

If you're looking for a bag, I highly recommend it.