I think you already have your answer. You know how to trim the boat in it's current configuration so it doesn't weathercock. Calculate the center of gravity of the movable pieces, i.e., you, your wife, the ice chest, any other heavy gear yoiu normally bring. If you maintain the same center of gravity when you relocate the cockpits, you should maintain the boat's handling. I'm sure some of the engineer types hanging around can help you out with CG calculations.