Sorry for the long post, I'm just hoping to pare down the questions I've read in similar threads... I'm in my mid 50s and hunt archery elk and deer as a resident in north Idaho. I've been using the Kuiu Pro 3600/5500LT for the past few seasons; 3600 for 80% of my hunting (from basecamp/ daytrips) and the 5500 for the 20% of my pack-in hunts. I have a pack on my back over 150 days per year between hunting and training. I love the layout of the bags and love the weight and fit of the Kuiu for most of my basecamp hunting and fast/light trips, but whenever I put over 30 lbs in the pack it is uncomfortable. Over 40lbs is not fun at all. Training hikes and pack in/out with weight are not fun, but not because of the exercise. I feel like the pack is shifting continually and just doesn't seem to carry weight well. Here is my question for those of you who have had both: Is the K4 really that much better? I know all heavy packs suck, but since 80% of my hunting is light, would I really get a huge benefit upgrading to the slightly heavier K4 3600/ 5000? In my 30s and 40s, and especially in my 20s right out of the USMC, I would just suck it up, but things tend to get a little more silly in my mid 50s, so I am looking for the best of both worlds. I'm really interested in opinions from those who have had both Kuiu and K4 (SG doesn't fit me well and I didn't like the Kifaru I tried, and I'm not interested in getting a K3). I am aware of Exo's return policy, I'm just trying to avoid the debate with my wife (aka "Knuckles") before I go down that road. Your thoughts?