Hi there,
I'd suggest a semi-rectangular bag. It's kind of hybrid between a rectangular and a mummy bag. They tend to be big enough to move around in, but small enough to warm up quickly. Unless you're a duck, I'd keep away from down(in the bwcaw anyway). There is a myriad of different "fills" for synthetic bags.
Qualofill and Hallofill are generally considered a last generation fill. A Hallofill fiber has 4 chambers in it. Picture a circle with an X in it. Hallofill is generally lighter than Qualofill but doesn't retain its shape as well.
A Qualofill fiber has 7 chamber's in it. Picture a dough-nut with 7 section around the center hole. Qualofill is heavier and doesn't pack as well, but does retain it's loft and does insulate a bit better.
The new generation of fills are Primaloft and Polarguard
3D. They're both a single strand extruded fiber that pulls in all directions and then regains it's shape. This is the latest and greatest out there.
I've had a Quallofil bag for a couple of years now and love it. You can generally find any of these bags at REI or Galyans. Sierra Designs and REI make very good and affordable bags.
Air Mattress are evil. Like Catbert evil. Get a thermarest, they'll work much better and insulate better than an air mattress. An air matress will pull body heat to the ground and disipate it out the sides of the mattress, air and plastic alone don't insulate well enough. Thermarests have a foam barrier that won't allow much of a heat transfer. If you do have a thermarest and it leaks, put a couple of inches of water in tub and submerge it. Look for the bubble and mark the spot. REI has Thermarest repair kits that work slicker than goose snot.
I hope that helps.
Peace.

Posted by Lucky on August 11, 2000 at 13:04