The reason I went to the big bag is I had a MR crew cab and with 5000 (+/-) inches it wasn't enough when you put 2/3 of boned out elk in it! ;-). You had to strap all your gear outside like a vagabond. Yes it was freaking heavy. 9 hours to go 6 miles downhill.
Also, the load lifters now sit correctly with the real bag.
Yes I was fatter a few years ago. That was my first backpack hunt. :-)