2B is a perspective view of a roof support of the shell frame of FIG. 2A.FIG. 2C is a perspective view of a floor support of the shell frame of FIG. 2A.FIG. 2D is a cross-section of a portion of the extension frame and shell frame showing the relationship of telescoping members.FIG. 2E is a perspective view of the extension frame of FIG. 2A.FIG. 3A-3F are perspective blow-up views of a portion of