The car and the subject have already been discussed in some detail here:
http://ecomodder.com/forum/showthrea...aks-18528.html
That said, I still think that the experienced aerodynamicsist all argue that the greatest gains are at the back. Read Hucho. It is true that even Hucho argued that significant aero improvements could be had by attention to detail in the front, A pillars, mirrors, wheelwells, etc. but he showed his greatest experimental gains in the back.
The reason that the Malibu didn't achieve higher gains at the rear is that they didn't try very hard there. Significant gains at the rear require a sloping roofline(reduced rear headroom), tapered sides(reduced trunk space), gradual taper to rear glass(reduced visibility), extended length(weight and driving difficulties). The Malibu is slanted at the family cruiser market. In that context, it doesn't do too badly. Give the stodgy old GM some credit for at least concentrating on aero at last. Certainly they can do more.