It all depends on the locations of the loads on the truss. The truss may be supporting a point load only at the peak, it may be supporting multiple purlins, it may be supporting SIPS spanning between trusses. The bottom chord may or may be not be supporting attic loads. For some configurations, the tension in the bottom chord is increased by a third if the chord is raised 1/4 of the truss depth; the tension is doubled if it is raised half way up; and the tension is quadrupled if it is raised 3/4 of the way up.
