Helping out here...(I hope). A plug for this pack.
This is a phenomal pack for day hunts and multi-day backpack hunts if you are going light.
I own that same pack and use it for wilderness archery elk from a wilderness base camp. I love it for that. I live in WA state and mostly do my wilderness hunts in the Rockies.
IMO, the pack is a bit heavy for a day pack but you are using it for its overall utility and ability to carry a heavy load, not just for water, lunch and rain gear. For its defined purpose it isn't heavy - its your brother. I take the lid off when not needed. I have lighter packs suitable for a single day or one night from base camp - but I prefer the K4 3600.
I've had a lot of hunting packs over the last 40 years or so of wilderness hunting and this is my favorite.
Right now I'm loading mine up to see how many days of backpack hunting I could cover with that size pack. I believe Mark Huesling (EXO) has used that size for a longish multi-day backpack hunt. From my perspective, it loads like a pack that is larger than 3600. Price looks fair to me, but what do I know?
I plan to sell my somewhat larger K3 version later this year because I don't need both...that and my K4 3600.