: The plan is to camp mostly, but stay in hotels occasionally. I estimate that
: the trip should take 4 - 5 weeks, depending on how high barge traffic is
: in the locks.

Hi - For a long time I considered a similar trip, and came to the conclusion that I definitely did NOT want to spend many hours a day, day after day, for 4-5 weeks, in the near immobile sitting position that a kayak would force me into! Subsequent shorter floats has only strongly confirmed this for me.

My thought is that perhaps you should consider a S&G rowboat or canoe. An open boat will let you slouch/sprawl/stretch/lie down/move about/get to your stuff/pee/etc to your heart's content. You really won't be doing much of that in a kayak - and when your butt goes to sleep, your options are pretty limited!

And, while many kayaks are relatively stable, they are less stable by far than most (non-racing) canoes or rowing craft. Ergo, you'd be concentrating much less on merely staying upright in one of those. {I do recognize that this becomes second nature after a while, though}
A kayak is easier to carry, yes - though not if it's loaded. Canoes often don't weigh much more than a kayak - or even less - or you can build simple, functional and good looking 14' rowing boat that weighs in at only about 70lbs.

I'm not saying that you 'couldn't' kayak that far, but you might enjoy the trip a LOT more in some other type of boat!

Check out Jim Michalak's wide variety of plywood rowboat designs - especially his roar2, robote, river runner, oaracle, qt skiff, or even his Larsboat. There are many others.