What's a U-Pac?
The name comes from the shape of the bag, like the letter "U," not the fact that "you pack" it. The shape makes it easy to hang over a seat or go around an obstacle, like a passenger or a tail trunk..
What Kind is Best?
Two-up riding makes the most demands because of the amount of gear two people need. One solution is a bag shaped like a horizontal U. The base of the U sits on the rear rack. The legs of the U point forward, straddling the seat and resting on the bike's saddlebags. This lets the passenger sit in the crotch of the U, using the legs of the U as armrests. A company that make these bags is Jo's Custom Creations (www.josupac.com, 757-877-7803). The bags range in size from small to humongous, fitting everything from sport bikes to big tourers.
If you ride solo, you can use the U-shaped pack, and can make even more storage space by nestling another bag in the crotch of the U. There are small bags designed just for this purpose. But what if you like having a lockable tail trunk to supplement your saddlebags for carrying valuables? A bag that fits this need is also U-shaped, but inverted. The base of the U rests on the passenger seat between you and the trunk, with the legs of the U extending down to rest on the saddlebags, resulting in a very stable arrangement. RevPack (revpack.com, 800-766-2461) and Mag's Bags (www.magsbags.com, 888-723-1504) offer this style of bag. The RevPack bag has a handy carrying handle. An unusual feature of the Mag's Bags is that they're available in a funky truck tarp material in addition to the usual Cordura.
An alternative is to have the bag face "backwards," as shown in the photo. The legs straddle the tail trunk, rather than resting on the saddlebags. This can result in more capacity, and is the option I chose. Because it wasn't a standard model, I had Jo's Custom Creations make me one that would accommodate the tail trunk in the crotch of the "U.". The bag is a standard overall width, but I asked Jo to square off the corners, which makes the bag a lot more versatile for the long items (chair, tent poles, mattress) that I carry. The zippers run around three sides so, like the Mag's Bags, it's easy to pack.
If straight duffle bags are more your thing than U-Pacs, consider the Helen TwoWheels "system." I bought a couple of Helen's bags, and like them. They are a very high-quality improvement on the bungee-everything-together system. It all makes for a good-looking setup, but the only one I've used much personally is the "miscellaneous" duffle bag, which I can tie on top of whatever pack I happen to be using, to provide even more space.. In addition, the tie-down straps she sells are excellent, and I continue to use them as back-up attachment straps for the RevPack and U-Pac.
The Bottom Line
As with most things, it really does depend on what you're carrying. If you ride two-up and don't have a trailer, Jo's standard U-Pac looks like the best bet for carrying all those extras. If you ride solo, it depends on the volume -- and on the length -- of what you're carrying. Measure your tent poles and your folding chair, and see if they will fit loosely within the dimensions of the bag. In my case, a variation on Jo's bag gave me the greater width I needed for my folding chair (at 29+ inches, the MagsBag and RevPac are too short for it), and the volume I needed for all the "stuff" I carry. But, as they say, your mileage may vary.
One thing you won't have to worry about is quality. All the bags mentioned here are thoughtfully designed and sturdily constructed of Cordura nylon. They're made and sold by small businesses, which thrive on customer satisfaction and the referrals this satisfaction brings.