: Try this exercise with either Kayak Foundry or BearboatSP or any
: program that does stability curves. Design a two kayaks, one
: which is 1" narrower at the waterline than the other. Do
: anything you want with the hull shape / cross-section and you
: will find that you cannot make the wider boat less stable (using
: classic stability curves) than the other. At 1/2" it is
: damn hard to do.

Sure you can. I just took at boat I use for purposes like this. Not a practical design I admit. It is 23" wide and flat bottomed and hard chines. Like a plywood boat.

I took this design and altered it to 24.093" wide at the water line. I didn't spend much time on it so I am not exactly at 1" larger. I made it with a rounded bottom and soft chines.

Just with my quick creation at 250 lb displacement for both boats (that is what I typically use) the 24" round bottom boat has slightly lower numbers than the 23" wide boat. Not dramatic but is it less stable and I am sure if I wanted to work at it I could make lower that.

So I respectfully disagree.
If you want the Freeship files I will share them.