I have the Eureka Spitfire 1 and have just enough room on the side for my 65L pack if its somewhat empty. I'm 6'1" and 195. There is enough room under the flap just outside. I think the key for me is keeping it light and getting by with less. Lots of good advice here and maybe trying a shorter thruhike will give you a better idea of what to expect. Surprising of how much stuff we don't need out there... Enjoy your adventure...