The GMC Aero Astro is a C.O.E. (Cab-Over-Engine) Vehicle which incorporates the use of add-on plastic body panels to achieve a more aerodynamicly efficient truck-tractor. These panels are made of low pressure-low modulus unreinforced RIM plastic and FRP (Fiber Rein-forced Plastic) using RTM (Resin Transfer Molding) fabricating techniques to obtain Class ‘A’ surfaces. The RTM process is unique since the reinforcement is integrally molded to the outer skins in a one step operation. The RIM (Reaction Injection Molded) panel is designed to collapse into a low profile sidewall when the dragfoiler is dropped into the lowered position. However, this same panel would have to expand and remain rigid enough to minimize cross wind effects in the raised position.This paper describes how these panels were developed for the Aero Astro, and how they would negotiate the multi-mission requirements for fuel efficiency.