For whitetail hunting around the Midwest if I'm using screw in climbers I use a possibles bag built off the design Dad started using in the '60's - think plain type possibles bag, leather, no extra pockets etc .... this is a simpler is better deal. Probably 18inches wide, 8-10high, 5 deep. Now that I'm using ladder sticks more I've been using a small brown duck "messengers bag" I got from Amazon for like 12 bucks - it has a couple zipper pockets, and is probably 8in wide, 11 high, 3 deep. Plenty of room for stuff for a stand sit.... maybe it is a "Murse" but it works great, and is out of the way. You don't need all the crap you own to sit in a tree for 3 hours.
When I started going out West in the early 90's I paid attention to what locals and woodsman types out there used... not fancy dancy packs with space age components.... but sturdy pack frames and appropriate pack bags for the load carried. To that end I use a BullPac - freaking bombproof and it will carry WAY more than you or I will be able to pack. You CAN'T overload this frame. I use a waterproof canvas duffel type pack bag for packing in my gear, and when it's time to haul out an elk I just lash the meat bags on a load at a time and pack it out. This pack frame has covered a lot of miles and it will outlast me. It is ugly and plain, but made to use in the mountains, not look good in a catalog or on a model's back in an advertisement.
R