I have an AGC Cub, too.
I despise having a bunch of stuff hanging off my neck all day. The only two things worse are getting caught needing binoculars having left them in camp or having them along but banging on you all day because they are hanging from a strap. Thus, the Cub.
I don’t have anything to add re contents. I have given some thought to order of relative importance, since I really, really don’t want to overload this thing. I consider the critical stuff as follows:
One of those plastic, noisy whistles with a compass and magnifying glass
Licenses, etc.
Headlamp and spare batteries
Something to clean lenses
Spare ammunition
Zip ties (because zip ties and duct tape are not optional anywhere,anytime)
I carry a Havalon, spare blades, surgical gloves, a few wet wipes, lighter, film canister with cotton soaked in petroleum jelly and a few paper towels loaded in a gallon ziplock in one thigh pocket and a water bottle in the other, so this is basically a list of what’s on me if I ditch the daypack.
My two rather large issues relate to adjusting all this from eastern whitetail to elk in big bear country for a hunt this fall. My small Leupold rangefinder fits nicely in the Cub’s front pocket, but my much preferred Leica won’t fit. Then there’s the bear spray. Pouches for these just don’t play well with the skinny straps.