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i notice it's on a external frame pack, so some modification might be needed to hang a Duluth style pack but that's a minor thing?

Yes it is a minor thing.  The two ropes could be attached to each other with the food container also attched at that point as you do now, hanging below those ropes. The big difference is the container is raised by taking the slack out of the "horizontal" ropes, not by pulling down on a rope attached to the middle of the horizontal rope. Try it and see how much better it works.