Thanks for the feedback! I will look into bridges and see if there's something I can do about that.

i think its got a lot to do with deep water depth a 3 span on shallow water works fine,but on a deeper river its a no go even after laying castle foundations below to do the old game trick of them thinking they were supported.I would also advise builders to go 2 wall sections high before fitting a 1st floor ceiling as the ceiling placed on a 1 high wall overlaps the top of the wall and causes problems,ut snaps into place easily on a 2 section high wall.