Funny, I actually purchased all 3 of those packs in my quest for the perfect day pack (and I live in Hawaii).
I purchased the Shape Charge first. After all my research I thought it would be the perfect one based on features and feedback from others. My friend has a Door Gunner that I love, but since they don't make them anymore that wasn't an option. Unfortunately, I hated the Shape Charge the minute it arrived. For me, the frame was super uncomfortable. It was way overbuilt, bulky, and heavy. It really wasn't going to work for me here. I ended up sending it back, losing over $100 in shipping charges that left me with a pretty sour taste in my mouth. Oh well, paradise tax.
I bought the SG Avail 2200 next. I liked it well enough, but the lack of water bottle pockets, placement of the hydration port, arrangement of the many many straps, the belt configuration, tendency to barrel when loaded full, and more, left me less than impressed. Let me come back to this in a moment.
I bought the Kuiu Ranger 2200 on a pretty good sale. Figured I'd give it a try. I had the Venture 1800 before, which I really liked for its layout and materials, but the frame was uncomfortable. I bent the aluminum stays in the Venture to make it much better, but a big problem I have with Kuiu day packs is that the frame and pack extend several inches below the hip belt causing the pack to ride hard into the top of my butt. I hate that. Maybe some people like that? Idk, ymmv. The Ranger has a very similar layout and materials to the Venture but a much more comfortable frame. I like it except that it still suffers from that extension below the hip belt. I'll generally only use it when I'm wearing a thick coat which keeps the frame from riding on top of my butt. I may do some modifications to the bottom to make it more comfortable for me, because it otherwise is a pretty decent pack for my uses here in Hawaii.
After trying out the Ranger, I decided to give the Avail another go. With a bunch of modifications, I'm starting to like it more. First, I swapped out the hip belt. I'm using the belt from a 5.11 tactical skyweight 24l pack. For hipbelt pockets I pulled my exo mtn gear pockets off my K4 that I only use for longer hunts. I also cut a small rectangle from a thick yoga mat to beef up the lumbar pad. It's just wedged in there with the belt. I pulled out the frame and added a curved aluminum bar to the frame sheet at the same position as the top compression straps to help keep it from barreling. That helped a lot. I opened up the top seam to allow my water bladder hose to pass out the top so it could go over my right shoulder and not snag bushes or my bow string. I pulled a bunch of the buckles and straps off and only have the ones I need. I may actually cut some more straps and loops off that are really just extra tangle spots (for my use case, specifically. Others may have use for these in different environments). At this point, I like this pack fairly well. I've used it for travel several times. I got the Access bag, and when I get on the plane I put the stuff I want in my seat in the Access bag. When I get to my seat, the main pack goes up above and I put the Access bag under the seat in front of me. Water, headphones, charger, book, snacks. Really all I need.
I took the Avail on an archery deer hunt to Lāna'i recently. Shot a doe with my longbow and butchered it out and put the roughly 20lbs of meat in the bag and walked very comfortably the mile back uphill to the truck. I think for now I'm happy with this pack in general, unless a Door Gunner shows up somewhere. I've done some training hikes recently with 15-20 lbs in the pack and it carries nicely. Sure wish it had stretch pockets on the outside though.
I'm picky when it comes to packs, if you couldn't tell. Really just comes down to comfort for me, I'm happy with a wide variety of features. Hope these thoughts help.
