I hunt with a large day pack that is mostly empty, and pack game with an aluminum frame similar to the method used by Rob in VT (above). The only time I take a large pack bag is when I am setting up a spike camp or hunting on the move with just a sleeping bag, food, and water. I spent much of my misspent youth backpack hunting the Rocky Mountains for elk and/or mule deer and I have packed quite a few out. When you do buy a big pack pay close attention to the weight of the empty pack. The large internal frame packs do balance the load better on steep slopes but I need an external frame to carry heavy loads without getting too soaked with sweat from the pack hugging my back.
I like my outer shell clothing to be just a bit loose. Sometimes it gets so blasted cold that I end up wearing a bulkier insulating layer than planned.