Mountain Hardwear Expander
So what to do? As you note, Joe, several companies make "expanders," which attach to a bag's zipper and act like a big gusset. Mountain Hardwear, for instance, sells what it calls simply the Sleeping Bag Expander ($55; www.mountainhardwear.com), which is a down-filled device that adds eight inches of girth (at the shoulders) to any bag with a number eight YKK zipper. Which is most of them. And you can use it with either a down or synthetic bag, so don't worry about that. Big Agnes makes a similar product, called the Wedgie, with PrimaLoft synthetic fill that sells for $49 (www.bigagnes.com).
For that matter, if you'd rather just get a bigger bag, Big Agnes' Lost Ranger ($199) is nearly twice as wide as most mummy-style bags. Big Agnes makes their bags with an uninsulated "bottom"as in, you insert a sleeping pad into that area to add insulation beneath you. So the three-pound weight is not bad for a 15-degree bag. Or Marmot's Sawtooth is an extra-wide bag (70 inches at the shoulder) made in the traditional insulation-all-around style. It's $239, filled with down, and rated to 15 degrees (www.marmot.com). REI's Syn Cat bag ($119; www.rei.com) puts wide-bag comfort into an affordable, synthetic-fill bag.
Check out Outside's Gear of the Year winners in the 2005 Buyer's Guide , then get yourself a copy of the issue, on newsstands now!