Wanted to clarify my position on backpacks in the tree: I will always take the smallest and lightest I can get away with where I can comfortably carry what I need to. I am almost always carrying in at least one layer plus hunting gear because I always sweat on the way in, so something like a shape charge is probably ideal most of the time. I've been using the 22 Mag because I don't have the shape charge yet, but I do much prefer it to the Stryker XL. I really didn't see any advantages to the Stryker because the 22Mag has more bag capacity and has a meat/load shelf if you need it, I never have. Didn't take me long to sell it and go back to the 22.
With that said, occasionally the bigger bag does get used. A couple weeks ago I did a mile or so hike in with elevation gain in the mountains of NH where it was COLD, so I was carrying all my saddle gear, plus Bibs, plus heavy puffy, plus stratus jacket, coffee, snacks, all in the pack. In that case, the Hoodlum got the call.
No issue for me using a frame pack in the tree, but if you don't have any other trees around or any backdrop, you are going to stick out more. This 100% depends on where you're hunting, what time of year, etc.