I went on an elk hunt with a bunch of new hunters in October. They all went to Cabela's or Sportsman's Warehouse and bought high end packs. By the second day, they were all looking to lighten their packs. When I was young, I carried a 5 lb Army surplus pack with a steel frame. It was very comfortable, but also heavy. It was steel, canvas, and leather, and it still only weighed 5 lbs. I can't believer that with modern materials, packs weigh over 5 lbs. What I'm saying, is go as light as you can.
When I backpack in the summer, I carry a 20 oz. pack. It is big enough for a week long trip.
If you bone out your game, there is no need for a frame. The meat conforms to your back, and is comfortable. The comfort issue is solved by carrying your pack for weeks before the hunt. As a kid, with homemade backpacks with no padding on the straps, and no hip belt, I found that after 3 days, it was comfortable. The best way I've found to get in shape for a hunt is to put 45 lbs. in your pack and walk 3 to 5 miles a day with it. After a week or so, you don't feel the straps anymore. I get by with a $20 pack I bought at a gun show. I packed out a cow elk in two trips a few years ago. It was hard on my knees, but not my back or leg muscles.
