Of the possibilities listed, I'm only familiar with the Souris River Quetico 18.5' and 17'.  A Quetico 18.5' has lots of room, and should suffice for your journeying.  However, if you love the MNII, you might prefer the MNIV.  The loading should be done depending on wind conditions to get the stern or bow slightly heavier (lower in the water) towards the direction the wind is blowing from.  I like to bring a large day pack that weighs about 30 punds, that can be stowed behind the stern paddler or moved to the bow when paddling in a headwind.