Do you know how much food you need for 4 weeks, or are you just going to fill the pack until full? I would suggest you figure out exactly how much food you need, and then figure how to make it smaller in volume. Then figure the exact volume you need with all your stuff and get a pack to hold it all. And if it won't fit in your Ibex 80, you need to figure how to take less stuff. That pack is HUGE.
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