I would say to paddle the boat more before deciding. Play with the seat location, try loading it a little, get used to it some more.

Advantage: If you are unsure what to do, usually patience will make the solution clearer. You dont need to make major modifications right away. You can get a better feel for the percieved severity of the problem.
Disadvantage: It may not solve anything, and it may be harder to add components after the boat is finished.

Of the three, I like the skeg better; rudder is kind of nice but also can be a PITA. I'm not sure a 3/4" keel strip will do much, but it might, and it would be easy to remove if you wanted to go to a rudder or skeg later.