Will be hiking Whitney with a group of four next week. We will be doing a three day hike. Any info would be helpful. How are the water sources? If I carry three liters of water in my water bladder, it makes my pack 33 lbs.... would like to lighten the load. Any tips on that? Also a little nervous about the narrow area's on the trail, where exactly are they and how bad are they...? Thanks in advance :-)