The technical merit of the VSS development is to enhance aircraft maneuverability, while reducing drag, radar cross section and aircraft weight, with extended range. With the proven feasibility of the Variable Stiffness Spar (VSS) application to F-18 PRM in Phase I, the ZONA team now proposes a comprehensive VSS developmental program for Phase II, involving three major efforts. First, ZONA Technology (ZONA) will conduct ASTROS* using the wing-body and the transonic aerodynamics options in ZAERO and CFD verification for VSS design/analysis of a full scaled F-i8 PRM. To further enhance the roll performance, ZONA will further explore two optimum schemes of VSS, namely, the VSS/Torsion Free (TF) and the Time Varying VSS (TVS). Second, NASA/LaRC will conduct the wind-tunnel (WT) VSS model design/fabrication and testing in NASA TDT. ZONA will provide ASTROS* support for the VSS model design whenever appropriate. Third, ZONA will develop a VSS Design/Analysis Guidelines Packet based on the roll performance database obtained from ASTROS* solutions and NASA TDT data. To initiate the anticipated activity in Phase III, ZONA will use its IR&D to fund Boeing and SwRI for investigations of structural and control integration issues of VSS/F18 PRM. Our technical goal is to render the VSS/F-18 PRM as a flight technology demonstrator in Phase III.