Regarding Truss instability out of the plane, I was always wondering about if the concept should be studied or explained during engineering formation. To analysis a truss structure in some manner it is not difficult task. As long external loads are located at strucute joints (members stressed mainly by axial forces) and support allows to use Statics Law to get reaction values, just a simple forces balance it every joint should be enough to define interanal axial forces. Only during professinal career you realize that outplane buckling is the governing trouble to be solved
