Right on. I am assuming that you mean keep the pack dry while in camp-not on the trail. I have been using a golite poncho tarp for a year and it kept me and my gear dry. I had to use a bivy to keep splatter off my bag, and the gear goes behind me. Actually I use a golite jam2 and I stuff it with my extra clothes and use it as a pillow. I guess that saves space. I just got a Sierra Designs Oragami 2 UL and I love it. So much room for 28 ounces (plus 5 stakes and a hiking pole). It is so versatile in its possiblities for set up. There are many configurations. I can sit up in it and stay in my bag while I cook. I have been setting it up with a 48" height to block more winter wind, but it can be set up higher. The first time I used it was mid 30's, so I set it up 58" high witht the hilink pole and I could sit up straight while on my knees. But it is the roominess that I love. The fabric is similar to that used on their tent flys. It is sturdier than silnylon. I already had a wrist sized limb fall on it in a strong wind storm, and other than a light colored scar there was no damage. I think silnylon would have torn under that force. Oh yeah, its DRY, and during that wind storm I thought my treking pole was gonna bust or bend and the shelter was shaken, pushed and tugged in all directions, but no damage and no problems all night long. Except that after that limb fell I had a hard time sleeping.

http://www.sierradesigns.com/tarps.display.php?id=526

http://www.sierradesigns.com/pdf2006/origami_configurations.pdf