You would surely know more about what is possible than me since you have actually made one. My theory was that the lack of tenons on the ends would allow putting the pieces together to test the angles before inserting the loose tenons, but I realize that theory and reality can be quite different things. I would like to make one of these stools though as I think they are really special. I love the seat on yours and coincidentally I recently bought a 2-1/2" thick plank of purple heart which after seeing yours would be perfect for the seat.
Mike, an American living in Norway