Currently I own a Gregory Z55, it's a nice backpack. The specs say it weighs 4+ lbs but I just don't feel it's correct, it actually seem much lighter. Anyhow it has an inside pocket for a hydration bladder that I don't use. I just don't need to be carrying so much water when in the Sierra. I made a few slight modification to carry water up front on the straps. The idea is not mine I got the idea from a fellow fly fisher Richard Cullip. Richard had a similar carrying system. I thought it would be a good idea to post some of the photos I took of my own modifications that I made to my own backpack.
This image above is of one of the shoulder straps with a shock cord looped and tied to the shoulder strap. The shock cord is placed here to keep the water bottle from swinging while walking. Super easy to do, I recycled the shock cord from an old cycling jacket that I never use anymore.
This is blue para cord that has all the inside strands removed to lighten up the cord and make it easier to sew. I sewed the cord vs tying a knot to try and get a cleaner look. I hope it will hold up over time. If it doesn't I guess I will have to go with a knot.
This is what it looks like finished and ready for the water bottle. I'm using recycled Gatorade bottles for carrying my water, I believe they weigh 1.5 ounces which is very nice. Oh the plastic hooks were cut off the back of my pack, I think they were supposed to be used for carrying an ice ax, I don't carry one and don't plan on carrying one so off they went.
The end results with a full water bottle above, and two Gatorade bottles below, one full and one empty. I like it so far walking around the house, need to take it back on the trail and really test the system out.
Hope this is helpful to anyone looking for an easy modification to their backpack.